Single-instruction-multiple-data processing using multiple banks of vector registers

ABSTRACT

A vector processor includes two banks of vector registers where each vector register can stored multiple data elements and a control register with a field indicating a default bank. An instruction set for the vector processor includes instructions which use a register number to identify a vector registers in the default bank, uses a register number to identify a double-size vector register including a register from the first bank and a register from the second bank, and instructions which include a bank bit and a register number to access a vector register from either bank.

CROSS-REFERENCE TO RELATED APPLICATION

This patent document is related to and incorporates by reference, in their entirety the following concurrently filed patent applications:

U.S. patent application Ser. No. 08/697,102, filed Aug. 19, 1996, entitled "Multiprocessor Operation in a Multimedia Signal Processor;"

U.S. patent application Ser. No. 08/699,597, filed Aug. 19, 1996, entitled "Single-Instruction-Multiple-Data Processing in a Multimedia Signal Processor;"

U.S. patent application Ser. No. 08/699,280, filed Aug. 19, 1996, entitled "Efficient Context Saving and Restoring in Multi-Tasking Computing System Environment";

U.S. patent application Ser. No. 08/699,295, filed Aug. 19, 1996, entitled "System and Method for Handling Software Interrupts with Argument Passing".

U.S. patent application Ser. No. 08/699,294, filed Aug. 19, 1996, entitled "System and Method for Handling Interrupts and Exception Events in an Asymmetric Multiprocessor Architecture";

U.S. patent application Ser. No. 08/699,303, filed Aug. 19, 1996, entitled "Methods and Apparatus for Processing Video Data"; and

U.S. patent application Ser. No. 08/699,585, filed Aug. 19, 1996, entitled "Single-Instruction-Multiple-Data Processing with Combined Scalar/Vector Operations".

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to digital signal processors, and particularly processes for parallel processing of multiple data elements per instruction for multimedia functions such as video and audio encoding and decoding.

2. Description of Related Art

Programmable digital signal processors (DSPs) for multimedia applications such as real-time video encoding and decoding require considerable processing power for the large amount of data which must be processed within a limited time. Several architectures for digital signal processors are known. A general purpose architecture such employed in most microprocessors typically requires high operating frequencies to provide a DSP with sufficient computing power for real-time video encoding or decoding. This makes such DSP expensive.

A very long instruction word (VLIW) processor is a DSP having many functional units most of which perform different, relatively simple tasks. A single instruction for a VLIW DSP may be 128 bytes or longer and has separate parts which the separate functional units execute in parallel. VLIW DSPs have high computing power because many functional units can operate in parallel. VLIW DSPs also have relatively low cost because each functional unit is relatively small and simple. A problem for VLIW DSPs is inefficiency in handling input/output control, communication with a host computer, and other functions that do not lend themselves to parallel execution on the functional units of the VLIW DSP. Additionally, VLIW software differs from conventional software and can be difficult to develop because programming tools and programmers familiar with VLIW software architectures are scarce.

A DSP which provides reasonable cost, high computing power, and a familiar programming environment is sought for multimedia applications.

SUMMARY OF THE INVENTION

In accordance with an aspect of the invention, a multimedia digital signal processor (DSP) includes a vector processor which manipulates vector data (i.e. multiple data elements per operand) to provide high processing power. The processor uses a single-instruction-multiple-data architecture with a RISC type instruction set. Programmers can easily adapt to the programming environment of the vector processor because it is similar to the programming environments of general purpose processors with which most programmers are familiar.

The DSP includes a set of general-purpose vector registers. Each vector register has a fixed size but is partitioned into separate data elements of user selectable size. Accordingly, the number of data elements stored in a vector register depends on the selected size for the elements. For example, a 32-byte register can be divided into thirty two 8-bit data elements, sixteen 16-bit data elements, or eight 32-bit data elements. Selection of data size and type is made by an instruction which processes data associated with the vector register, and an execution data path for the instruction performs a number of parallel operations which depends on data size indicated by an instruction.

Instructions for the vector processor may have vector registers or scalar registers as operands and manipulate multiple data elements of vector registers in a parallel so that computing power is high. An exemplary instruction set for a vector processor in accordance with the invention includes: co-processor interface operations; flow control operations; load/store operations; and logic/arithmetic operations. The logic/arithmetic operations include operations which combine data elements from one vector register with corresponding data elements from one or more other vector registers to generate the data elements of a resulting data vector. Other logic/arithmetic operations mix various data elements from one or more vector registers or combine data elements from a vector register with scalar quantities.

An extension of the vector processor architecture adds scalar registers, each of which contains a scalar data element. The combination of scalar and vector registers facilitates extension of the vector processor's instruction set to include operations that in parallel combine each data element of a vector with a scalar value. One instruction, for example, multiplies the data elements of a vector by a scalar value. Scalar registers also provide a location for storage of a single data element to be extracted from or stored in a vector register. The scalar registers are also convenient for passing information between the vector processor and a co-processor having an architecture that provides only scalar registers and for calculations of effective addresses for load/store operations.

In accordance with another aspect of the invention, vector registers in the vector processor are organized into banks. Each bank can be selected to be the "current" bank while the other bank is the "alternative" bank. A "current bank" bit in a control register of the vector processor indicates the current bank. To reduce the number of bits require to identify a vector register, some instructions provide only a register number to identify a vector register in the current bank. Load/store instructions have an additional bit to identify a vector register from either bank. Accordingly, load/store operations can fetch data into the alternative bank during manipulation of data in the current bank. This facilitates software pipelining for image processing and graphics procedures, and reduces processor delays when fetching data because logic/arithmetic operations can be performed out-of-order with load/store operations accessing the alternative register bank. In other instructions, the alternative bank permits use of double-size vector registers which include a vector register from the current bank and a corresponding vector register from the alternative bank. Such double-size registers may be identified from instruction syntax. A control bit in the vector processor may be set so that the default vector size is either one or two vector registers. The alternative bank also enable use of fewer explicit identified operands in the syntax of complex instructions such as shuffle, unshuffle, saturate, and conditional moves that-have two source and two destination registers.

The vector processor further implements novel instructions such as average quad, shuffle, unshuffle, pair-wise maximum and exchange, and saturate. These instructions perform operations common in multimedia functions such as video encoding and decoding and take the place of two or more instructions which other instruction sets would required to implement the same operations. Accordingly, the vector processor instruction set improves the efficiency and speed of programs in multimedia applications.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram of a multimedia processor in accordance with an embodiment of the invention.

FIG. 2 is a block diagram of a vector processor for the multimedia processor of FIG. 1.

FIG. 3 is block diagram of an instruction fetch unit for the vector processor of FIG. 2.

FIG. 4 is block diagram of a scheduler for the vector processor of FIG. 2.

Figs. 5A, 5B, and 5C show the stages of execution pipelines for a register-to-register instruction, a load instruction, and a store instruction for the vector processor of FIG. 2.

FIG. 6A is a block diagram for an execution data path for the vector processor of FIG. 2.

FIG. 6B is a block diagram of a register file for the execution data path of FIG. 6A.

FIG. 6C is a block diagram for parallel processing logic units for the execution data path of FIG. 6A.

FIG. 7 is a block diagram for a load/store unit for the vector processor of FIG. 2.

FIG. 8 illustrates formats for an instruction set of a vector processor in accordance with an embodiment of the invention.

Use of the same reference symbols in different figures indicates similar or identical items.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 shows a block diagram of an embodiment of a multimedia signal processor (MSP) 100 in accordance with an embodiment of the invention. Multimedia processor 100 includes a processing core 105 containing a general-purpose processor 110 and a vector processor 120. Processing core 105 connects to the remainder of multimedia processor 100 through a cache subsystem 130 which contains SRAM 160 and 190, a ROM 170, and a cache control 180. Cache control 180 can configure SRAM 160 as an instruction cache 162 and a data cache 164 for processor 110 and configure SRAM 190 as an instruction cache 192 and data cache 194 for vector processor 120.

On-chip ROM 170 contains data and instructions for processors 110 and 120 and can also be configured as a cache. In the exemplary embodiment, ROM 170 contains: reset and initialization procedures; self-test diagnostics procedures; interrupt and exception handlers; and subroutines for soundblaster emulation; subroutines for V.34 modem signal processing; general telephony functions; 1-D and 3-D graphics subroutine libraries; and subroutine libraries for audio and video standards such as MPEG-1, MPEG-2, H.261, H.263, G.728, and G.723.

Cache subsystem 130 connects processors 110 and 120 to two system busses 140 and 150 and operates as both a cache and a switching station for processors 110 and 120 and the devices coupled to busses 140 and 150. System bus 150 operates at a higher clock frequency than bus 140 and is connected to a memory controller 158, a local bus interface 156, a DMA controller 154, and a device interface 152 which respectively provide interfaces for an external local memory, a local bus of a host computer, direct memory accesses, and various analog-to-digital and digital-to-analog converters. Connected to bus 140 are a system timer 142, a UART (universal asynchronous receiver transceiver) 144, a bitstream processor 146, and an interrupt controller 148. The above-incorporated patent applications entitled "Multiprocessor Operation in a Multimedia Signal Processor" and "Methods and Apparatus for Processing Video Data" more fully describe the operation of cache subsystem 130 and exemplary devices which processors 110 and 120 access through cache subsystem 130 and buses 140 and 150.

Processors 110 and 120 execute separate program threads and are structurally different for more efficient execution of particular tasks assigned to them. Processor 110 is primarily for control functions such as execution of a real-time operating system and similar functions not requiring large numbers of repetitive calculations. Accordingly, processor 110 does not require high computing power and can be implemented using a conventional general-purpose processor architecture. Vector processor 120 mostly performs number crunching that involves repetitive operations on data blocks common in multimedia processing. For high computing power and relatively simple programming, vector processor 120 has a SIMD (single instruction multiple data) architecture; and in the exemplary embodiment, most data paths in vector processor 120 are either 288 or 576 bits wide to support vector data manipulation. Additionally, the instruction set for vector processor 120 includes instructions particularly suited for multimedia problems.

In the exemplary embodiment, processor 110 is a 32-bit RISC processor which operates at 40 MHz and conforms to the architecture of an ARM7 processor including a register set as defined by the ARM7 standard. An architecture and instruction set for an ARM7 RISC processor is described in the "ARM7DM Data Sheet", Document Number: ARM DDI 0010G which is available from Advance RISC Machines Ltd. The ARM7DM Data Sheet is hereby incorporated by reference herein in its entirety. Appendix A describes the extension of ARM7 instruction set in the exemplary embodiment.

Vector processor 120 manipulates both vector and scalar quantities. In the exemplary embodiment, vector data processor 120 consists of a pipelined RISC engine that operates at 80 MHz. The registers of vector processor 120 includes 32-bit scalar registers, 32-bit special-purpose registers, two banks of 288-bit vector registers, and two double-size (i.e., 576-bit) vector accumulator registers. Appendix C describes the register set for the exemplary embodiment of vector processor 120. In the exemplary embodiment, processor 120 includes 32 scalar registers which are identified in instructions by 5-bit register numbers ranging from 0 to 31. There are also 64 288-bit vector registers which are organized into two banks of 32 vector registers. Each vector register can be identified by a 1-bit bank number (0 or 1) and a 5-bit vector register number ranging from 0 to 31. Most instruction only access vector registers in a current bank as indicated by a default bank bit CBANK stored in a control register VCSR of vector processor 120. A second control bit VEC64 indicates whether register numbers by default identify a double-size vector register including a register from each bank. The syntax of the instructions distinguishes register numbers identifying a vector registers from register numbers identifying a scalar registers.

Each vector register can be partitioned into data elements of programmable size. Table 1 shows the data types supported for data elements within a 288-bit vector register.

                  TABLE 1                                                          ______________________________________                                         Data Type                                                                             Data Size Interpretation                                                ______________________________________                                         int8   8 bits    8-bit 2's complement between -128 and 127.                           (Byte)                                                                  int9   9 bits    9-bit 2's complement between -256 and 255.                           (Byte9)                                                                 int16  16 bits   16-bit 2's complement between -32,768 and                            (Halfword)                                                                               32,767.                                                       int32  32 bits   32-bit 2's complement between -2147483648                            (Word)    and 2147483647                                                float  32 bits   32-bit IEEE 754 single-precision format.                             (Word)                                                                  ______________________________________                                    

Appendix D provides further descriptions of the data sizes and types supported in the exemplary embodiment of the invention.

For int9 data type, 9-bit bytes are packed consecutively in a 288-bit vector register, but for the other data types every ninth bit in a 288-bit vector register is unused. A 288-bit vector register can hold 32 8-bit or 9-bit integer data elements, sixteen 16-bit integer data elements, or eight 32-bit integer or floating point elements. Additionally, two vector registers may be combined to pack data elements in a double-size vector. In the exemplary embodiment of the invention, setting a control bit VEC64 in a control and status register VCSR places vector processor 120 in a mode VEC64 where double-size (576 bits) is the default size of vector registers.

Multimedia processor 100 also contains a set of 32-bit extended registers 115 which are accessible to both processors 110 and 120. Appendix B describes the set of extended registers and their function in the exemplary embodiment of the invention. The extended registers and the scalar and special-purpose registers of vector processor 120 are accessible to processor 110 in some circumstances. Two special "user" extended registers have two read ports to allow processors 110 and 120 to simultaneously read the registers. Other extended registers can not be simultaneously accessed.

Vector processor 120 has two alternative states VP₋₋ RUN and VP₋₋ IDLE which indicate whether vector processor 120 is running or idle. Processor 110 can read or write scalar or special-purpose registers of vector processor 120 when vector processor 120 is in state VP₋₋ IDLE, but the results of processor 110 reading or writing a register of vector processor 120 while vector processor 120 is in state VP₋₋ RUN are undefined.

The extension of the ARM7 instruction set for processor 110 includes instructions which access the extended registers and the scalar or special-purpose registers of vector processor 120. Instructions MFER and MFEP move data respectively from an extended register and a scalar or special-purpose register in vector processor 120 to a general register in processor 110. Instructions MTER and MTEP respectively move data from a general register in processor 110 to an extended register and a scalar or special-purpose register in vector processor 120. A TESTSET instruction both reads an extended register and sets bit 30 of the extended register to 1. Instruction TESTSET facilitates user/producer synchronization by setting bit 30 to signal to processor 120 that processor 110 has read (or used) a result produced. Other instructions for processor 110 such as STARTVP and INTVP control the operating state of vector processor 120.

Processor 110 acts as a master processor to control operation of vector processor 120. Using asymmetric division of control between processors 110 and 120 simplifies the problem of synchronizing processors 110 and 120. Processor 110 initializes vector processor 120 by writing an instruction address to a program counter for vector processor 120 while vector processor 120 is in state VP₋₋ IDLE. Processor 110 then executes a STRATVP instruction which changes vector processor 120 to state VP₋₋ RUN. In state VP₋₋ RUN, vector processor 120 fetches instructions through a cache subsystem 130 and executes those instructions in parallel with processor 110 continuing to execute it own program. After being started, vector processor 120 continues execution until encountering an exception, executing a VCJOIN or VCINT instruction with an appropriate condition satisfied, or being interrupted by processor 110. Vector processor 120 can pass results of program execution to processor 110 by writing the results to an extended register, writing the results to the shared address space of processors 110 and 120, or leaving the result in a scalar or special purpose register which processor 110 accesses when vector processor 120 re-enters state VP₋₋ IDLE.

Vector processor 120 does not handle its own exceptions. Upon executing an instruction that causes an exception, vector processor 120 enters state VP₋₋ IDLE and signals an interrupt request through a direct line to processor 110. Vector processor 120 remains in state VP₋₋ IDLE until processor 110 executes another STARTVP instruction. Processor 110 is responsible for reading a register VISRC of vector processor 120 to determine the nature of the exception, handling the exception possibly by reinitializing vector processor 120, and then directing vector processor 120 to resume execution if desired.

An INTVP instruction executed by processor 110 interrupts vector processor 120 causing the vector processor 120 to enter idle state VP₋₋ IDLE. Instruction INTVP may, for example, be used in a multitasking system to switch vector processor 120 from one task such as video decoding to another tasks such as sound card emulation.

Vector processor instructions VCINT and VCJOIN are flow control instructions which if a condition indicated by the instruction is satisfied, halt execution by vector processor 120, place vector processor 120 in state VP₋₋ IDLE, and issue an interrupt

request to processor 110 unless such requests are masked. The program counter (special-purpose register VPC) of vector processor 120 indicates the instruction address after the VCINT or VCJOIN instruction. Processor 110 can check an interrupt source register VISRC of vector processor 120 to determine whether a VCINT or VCJOIN instruction caused the interrupt request. Since vector processor 120 has large data busses and is more efficient at saving and restoring its registers, software executed by vector processor 120 should save and restore registers during context switching. The above-incorporated patent application entitled "Efficient Context Saving and Restoring in Multi-Tasking Computing System Environment" describes an exemplary system for context switching.

FIG. 2 shows the primary functional blocks of the exemplary embodiment of vector processor 120. Vector processor 120 includes an instruction fetch unit (IFU) 210, a decoder 220, a scheduler 230, an execution data path 240, and a load/store unit (LSU) 250. IFU 210 fetches instructions and processes flow control instructions such as branches. Instruction decoder 220 decodes one instruction per cycle in the order of arrival from IFU 210 and writes field values decoded from the instruction to a FIFO in scheduler 230. Scheduler 230 selects the field values which are issued to execution control registers as required for the execution stages of operations. Issue selection depends on operands dependency and the availability of processing resources such as execution data path 240 or load/store unit 250. Execution data path 240 executes logic/arithmetic instructions which manipulate vector or scalar data. Load/store unit 250 executes load/store instructions which access the address space of vector processor 120.

FIG. 3 shows a block diagram of an embodiment of IFU 210 which contains an instruction buffer that is divided into a main instruction buffer 310 and a secondary instruction buffer 312. Main buffer 310 contains eight consecutive instructions including the instruction corresponding to the current program count. Secondary buffer 312 contains the eight instructions that immediately follow the instructions in buffer 310. IFU 210 also includes a branch target buffer 314 containing eight consecutive instructions including the target of the next flow control instruction in buffer 310 or 312. In the exemplary embodiment, vector processor 120 uses a RISC-type instruction set where each instruction is 32 bits long, and buffers 310, 312, and 314 are 8×32 bit buffers and connected to cache subsystem 130 through a 256-bit instruction bus. IFU 210 can load eight instructions from cache subsystem 130 into any of buffers 310, 312, or 314 in a single clock cycle. Registers 340, 342, and 344 respectively indicate base addresses for the instructions loaded in buffers 310, 312, and 314.

A multiplexer 332 selects the current instruction from main instruction buffer 310. If the current instruction is not a flow control instruction and an instruction stored in instruction register 330 is advancing to a decode stage of execution, the current instruction is stored into an instruction register 330, and the program count in incremented. After incrementing the program count selects the last instruction in buffer 310, the next set of eight instructions are loaded into buffer 310. If the buffer 312 contains the desired eight instructions, the contents of buffer 312 and register 342 are immediately moved to buffer 310 and register 340, and eight more instructions are prefetched from cache system 130 into secondary buffer 312. An adder 350 determines the address of the next set of instructions from the base address in register 342 and an offset selected by a multiplexer 352. The resulting address from adder 350 is stored in register 342 as or after the address from register 342 moves to register 340. The calculated address is also sent to cache subsystem 130 with the request for eight instructions. If a previous call to cache control system 130 has not yet provided the next eight instructions to buffer 312 when required by buffer 310, the instructions previously requested are immediately stored in buffer 310 when received from cache subsystem 130.

If the current instruction is a flow control instruction, IFU 210 handles the instruction by evaluating a condition for the flow control instruction and updating the program count following the flow control instruction. IFU 210 is held up if the condition is undetermined because a previous instruction which may change the condition has not completed. If a branch is not taken, the program counter is incremented, and next instruction is selected as described above. If a branch is taken and branch target buffer 314 contains the target of the branch, the contents of buffer 314 and register 344 are moved to buffer 310 and register 340 so that IFU 210 can continue providing instructions to decoder 220 without waiting for instructions from cache subsystem 130.

To prefetch instructions for branch target buffer 314, a scanner 320 scans buffers 310 and 312 to locate the next flow control instruction following the current program count. If a flow control instruction is found in buffer 310 or 312, scanner 320 determines the offset from the base address of the buffer 310 or 312 containing the instruction, to an aligned set of eight instructions including the target address of the flow control instruction. Multiplexers 352 and 354 provide the offset from the flow control instruction and the base address from register 340 or 342 to adder 350 which generates a new base address for buffer 314. The new base address is passed to cache subsystem 130 which subsequently provides the eight instructions for branch target buffer 314.

In handling flow control instructions such as "decrement and conditional branch" instructions VD1CBR, VD2CBR, and VD3CBR and "change control register" instruction VCHGCR, IFU 210 can change register values in addition to the program count. When IFU 210 finds an instruction that is not a flow control instruction, -that instruction passes to instruction register 330 and from there to decoder 220.

Decoder 220 decodes an instruction by writing control values to the fields of a FIFO buffer 410 in scheduler 230 as shown in FIG. 4. FIFO buffer 410 contains four rows of flip-flops, each of which can contain five fields of information for controlling the execution of one instruction. Row 0 to 3 hold the information respectively for the oldest to newest instructions, and information in FIFO buffer 410 shifts down to lower rows when older information is removed as instructions complete. Scheduler 230 issues an instruction to an execution stage by selecting the necessary fields of the instruction to be loaded into a control pipe 420 including execution registers 421 to 427. Most instructions can be scheduled for out-of-order issue and execution. In particular, the order of logic/arithmetic operations relative and load/store operations is arbitrary unless there are operand dependencies between the load/store operations and the logic/arithmetic operations. Comparisons of the field values in FIFO buffer 410 indicate whether any operand dependencies exist.

FIG. 5A illustrates a six stage execution pipeline for an instruction which performs a register-to-register operation without accessing the address space of vector processor 120. In an instruction fetch stage 511, IFU 210 fetches an instruction as described above. Fetch stage requires one clock cycle unless IFU 210 is held up by a pipeline delay, an unresolved branch condition, or a delay in cache subsystem 130 providing prefetched instructions. In decode stage 512, decoder 220 decodes the instruction from IFU 210 and writes information for the instruction to scheduler 230. Decode stage 512 also requires one clock cycle unless no rows in FIFO 410 are available for a new operation. The operation can be issued to control pipe 420 during the first cycle in FIFO 410, but may be delayed by issue of older operations.

Execution data path 240 performs register-to-register operations and provides data and addresses for load/store operations. FIG. 6A shows a block diagram of an embodiment of execution data path 240 and is described in conjunction with execution stages 514, 515, and 516. Execution register 421 provides signals identifying two registers in a register file 610 which are read in a clock cycle during read stage 514. Register file 610 includes 32 scalar registers and 64 vector registers. FIG. 6B is a block diagram of register file 610. Register file 610 has two read ports and two write ports to accommodate up to two reads and two writes each clock cycle. Each port includes a select circuit 612, 614, 616, or 618 and a 288-bit data bus 613, 615, 617, or 619. Selection circuits such as circuits 612, 614, 616, and 618 are well known in the art and use an address signal WRADDR1, WRADDR2, RDADDR1, or RDADDR2 which decoder 220 derives from a 5-bit register number which is typically extracted from an instruction, a bank bit from the instruction or control status register VCSR, and instruction syntax which indicates whether registers are vector registers or scalar registers. Data read can be routed through multiplexer 656 to load/store unit 250 or through multiplexers 622 and 624 through a multiplier 620, an arithmetic logic unit 620, or an accumulator 640. Most operation read two registers, and read stage 514 is completed in one cycle. However, some instructions such as multiply-and-add instruction VMAD and instructions that manipulate double-size vectors require data from more than two registers so that read stage 514 is longer than one clock cycle.

During execution stage 515, multiplier 620 arithmetic logic unit 630, and accumulator 640, process data previously read from register file 610. Execution stage 515 can overlap read stage 514 if multiple cycle are required to read the necessary data. The duration of execution stage 515 depends on the type data elements (integer or floating point) and amount (number of read cycles) of data processed. Signals from execution registers 422, 423, and 425 control input data to arithmetic logic unit 630, accumulator 640, and multiplier 620 for first operations performed during execution stage. Signals from execution registers 432, 433, and 435 control second operations performed during execution stage 515.

FIG. 6C shows a block diagram of an embodiment of multiplier 620 and ALU 630. Multiplier 620 is an integer multiplier which contains eight independent 36×36 bit multipliers 626. Each multiplier 626 contains four 9×9-bit multipliers which are connected together by control circuitry. For 8-bit and 9-bit data element size, control signals from scheduler 230 disconnect the four 9×9-bit multipliers from each other so that each multiplier 626 performs four multiplications, and multiplier 620 performs 32 independent multiplications during a cycle. For 16-bit data elements, control circuitry connects pairs of 9×9-bit multipliers to operate together, and multiplier 620 performs sixteen parallel multiplications. For the 32-bit integer data element type, eight multipliers 626 perform eight parallel multiplications per clock cycle. The results of a multiplication provides 576 bits result for 9-bit data element size and 512 bits for the other data sizes.

ALU 630 can process the resulting 576-bit or 512-bit result from multiplier 620 in two clock cycles. ALU 630 contains eight independent 36-bit ALUs 636. Each ALU 636 contains a 32×32 bit floating point unit for floating point adds and multiplies. Additional circuitry implements integer shift, arithmetic, and logic functions. For integer manipulations, each ALU 636 contains four units capable of independent 8-bit and 9-bit manipulations, and capable of being linked together in sets of two or four for 16-bit and 32-bit integer data elements.

Accumulator 640 accumulates results and includes two 576-bit registers for higher precision in intermediate results.

During write stage 516, results from the execution stage are stored in register file 610. Two registers can be written to during a single clock cycle, and input multiplexers 602 and 605 select two data values to be written. The duration of write stage 516 for an operation depends on the amount of data to be written as a result of the operation and competition from LSU 250 which may be completing a load instruction by writing to register file 610. Signals from execution registers 426 and 427 select the register to which data from logic unit 630, accumulator 640, and multiplier 620 is written.

FIG. 5B shows an execution pipeline 520 for execution of a load instruction. The instruction fetch stage 511, decode stage 512, and issue stage 513 for execution pipeline 520 are the same as described for a register-to-register operation. The read stage 514 is also the same as described above except that the execution data path 240 uses data from register file 610 to determine an address for a call to cache subsystem 130. In address stage 525, multiplexers 652, 654, and 656 select the address which is provided to load/store unit 250 for execution stages 526 and 527. Information for the load operation remains in FIFO 410 during stages 526 and 527 while load/store unit 250 handles the operation.

FIG. 7 shows an embodiment of load/store unit 250. During stage 526, a call is made to cache subsystem 130 for data from the address determined in stage 525. The exemplary embodiment uses transaction based cache calls where multiple devices including processors 110 and 120 can access the local address space through cache subsystem 130. The requested data may not be available for several cycles after a call to cache subsystem 130, but load/store unit 250 can make calls to cache subsystem while other calls are pending. Accordingly, load/store unit 250 is not held up. The number of clock cycle required for cache subsystem 130 to provide the requested data depends on whether there is a hit or miss in data cache 194.

In drive stage 527, cache subsystem 130 asserts a data signal for load/store unit 250. Cache subsystem 130 can provide 256 bits (32 bytes) of data per cycle to load/store unit 250. A byte aligner 710 aligns each of the 32 bytes in a corresponding 9-bit storage location to provide a 288-bit value. The 288-bit format is convenient for multimedia applications such as MPEG encoding and decoding which sometimes use 9-bit data elements. The 288-bit value is written into a read data buffer 720. For write stage 528, scheduler 230 transfers field 4 from FIFO buffer 410 to execution register 426 or 427 to write the 288-bit quantity from data buffer 720 to register file 610.

FIG. 5C shows an execution pipeline 530 for execution of a store instruction. The instruction fetch stage 511, decode stage 512, and issue stage 513 for execution pipeline 530 are the same as described above. The read stage 514 is also the same as described above except that the read stage reads data to be stored and data for address calculations. Data to be stored is written to write data buffer 730 in load/store unit 250. Multiplexers 740 convert the data which is in a format providing for 9-bit bytes into a conventional format having 8-bit bytes. The converted data from buffer 730 and the associated address from address calculation stage 525 are sent in parallel to cache subsystem 130 during SRAM stage 536.

In the exemplary embodiment of vector processor 120, each instruction is 32 bits long and has one of the nine formats shown in FIG. 8 and labeled REAR, REAI, RRRM5, RRRR, RI, CT, RRRM9, RRRM9*, and RRRM9**. Appendix E describes the instruction set for vector processor 120.

Some load, store, and cache operations which use scalar registers when determining an effective address have the REAR format. REAR-format instructions are identified by bits 29-31 being 000b and have three operands identified by two register numbers SRb and SRi for scalar registers and a register number Rn of a register which may be a scalar or vector register depending on a bit D. A bank bit B either identifies a bank for register Rn or indicates whether vector register Rn is a double-size vector register if the default vector register size is double-size. An op-code code field Opc identifies the operation performed on the operands, and a field TT indicates a transfer type as load or store. A typical REAR-format instruction is instruction VL which loads register Rn from an address determined by adding the contents of scalar registers SRb and SRi. If a bit A is set the calculated address is stored in scalar register SRb.

REAI-format instructions are the same as REAR instructions except that an 8-bit immediate value from field IMM is used in place of the contents of scalar register SRi. REAR and REAI formats do not have a data element size field.

The RRRM5 format is for instructions having two source operands and one destination operand. These instructions have either three register operands or two register operands and a 5-bit immediate value. An encoding of fields D, S, and M as shown in Appendix E determines whether the first source operand Ra is a scalar or vector register; whether the second source operand Rb/IM5 is a scalar register, a vector register, or a 5-bit immediate value; and whether the destination register Rd is a scalar or vector register.

The RRRR format is for instructions having four register operands. Register numbers Ra and Rb indicated source registers. Register number Rd indicates a destination register, and register number Rc indicates either a source or a destination register depending on field Opc. All of the operands are vector registers unless bit S is set to indicate register Rb is a scalar register. Field DS indicates the data element size for the vector registers. Field Opc selects the data type for 32-bit data elements.

An RI-format instruction loads an immediate value into a register. Field IMM contains an immediate value of up to 18 bits. Register number Rd indicates the destination register which is either a vector register in the current bank or a scalar register depending on bit D. Fields DS and F respectively indicate a data element size and type. For 32-bit integer data elements, the 18-bit immediate value is sign extended before being loaded into register Rd. For floating point data elements, bit 18, bits 17 to 10, and bits 9 to 0 respectively indicate the sign, exponent, and mantissa of a 32-bit floating point value.

The CT format is for flow control instructions and includes an op-code field Opc, a condition field Cond, and a 23-bit immediate value IMM. A branch is taken when a condition indicated by the condition field is true. Possible condition codes are "always", "less than", "equal", "less than or equal", "greater than", "not equal", "greater than or equal", and "overflow". Bits GT, EQ, LT, and SO in status and control register VCSR are used to evaluate the conditions.

Format RRRM9 provides for either three register operands or two register operands and a 9-bit immediate value. A combination of bits D, S, and M indicate which of operands are vector registers, scalar registers, or 9-bit immediate values. Field DS indicates a data element size. The RRRM9* and RRRM9** formats are special cases of the RRRM9 format and distinguished by opcode field Opc. The RRRM9* format replaces a source register number Ra with a condition code Cond and an ID field. The RRRM9** format replaces most significant bits of the immediate value with a condition code Cond and a bit K. Further description of RRRM9* and RRRM9** is given in Appendix E in regard to conditional move instruction VCMOV, conditional move with element mask CMOVM, and compare and set mask CMPV instructions.

Although the invention has been described with reference to particular embodiments, the description is only an example of the invention's application and should not be taken as a limitation. Various adaptations and combinations of features of the embodiments disclosed are within the scope of the invention as defined by the following claims.

APPENDIX A

In the exemplary embodiment, processor 110 is a general-purpose processor which complies with the standard for an ARM7 processor. Refer to an ARM architecture document or the ARM7 Data Sheet (document number ARM DDI 0020C, issued Dec 1994) for the description of registers within the ARM7.

To interact with vector processor 120 processor 110: starts and stops vector processor; tests the vector processor state, including for synchronization; transfers data from a scalar/special-purpose register in vector processor 120 to a general register in processor 110; and transfers data from a general register to a vector processor scalar/special-purpose register. There is no direct means of transfer between a general register and a vector processor vector register. Such transfers require memory as an intermediary.

Table A.1 describes the extension to the ARM7 instruction set for vector processor interactions.

                  TABLE A.1                                                        ______________________________________                                         ARM7 Instruction Set Extension                                                 Instruction                                                                            Result                                                                 ______________________________________                                         STARTVP This instruction causes the vector processor to enter the                      VP.sub.-- RUN state but has no affect if the vector processor is               already in the VP.sub.-- RUN state. STARTVP is implemented                     as the processor-data operation (CDP) class in the ARM7                        architecture. No result is communicated back to ARM7, and                      the ARM7 continues its execution                                       INTVP   This instruction causes the vector processor to enter the                      VP.sub.-- IDLE state but has no affect if the vector processor                 is                                                                             already in the VP.sub.-- IDLE state. INTVP is implemented as                   the processor data operation (CDP) class in the ARM7                           architecture. No result is communicated back to ARM7, and                      the ARM7 continues its execution.                                      TESTSET This instruction reads a user extended register and sets                       bit 30 of the register to 1 to provide producer/consumer                       type of synchronization between vector and ARM7                                processors. TESTSET is implemented as the processor                            register transfer (MRC) class in the ARM7 architecture.                        The ARM7 is stalled until the instruction is executed (the                     register is transferred).                                              MFER    Moves from an extended register to an ARM general                              register. MFER is implemented as the processor register                        transfer (MRC) class in the ARM7 architecture. The ARM7                        is stalled until the instruction is executed (the register is                  transferred).                                                          MFVP    Moves from a vector processor scalar/special-purpose                           register to an ARM7 general register. Unlike the other                         ARM7 instructions, this instruction should be executed only                    when the vector processor is in the VP.sub.-- IDLE state. The                  result is otherwise undefined. MFVP is implemented as the                      processor register transfer (MRC) class in the ARM7                            architecture. The ARM7 is stalled until the instruction is                     executed (the register is transferred).                                MTER    Moves to an extended register from an ARM7 general                             register. MTER is implemented as the coprocessor register                      transfer (MCR) class in the ARM7 architecture. The ARM7                        is stalled until the instruction is executed (the register is                  transferred).                                                          MTVP    Moves to a vector processor scalar/special-purpose                             register from an ARM7 general register. Unlike the other                       ARM7 instructions, this instruction should be expected only                    when the vector processor is in the VP.sub.-- IDLE state. The                  result is otherwise undefined. MTVP is implemented as the                      coprocessor register transfer (MCR) class in the ARM7                          architecture. The ARM7 is stalled until the instruction is                     executed (the register is transferred).                                CACHE   Provides software management of the ARM7 data cache.                   PFTCH   Prefetches one cache line into the ARM7 data cache.                    WBACK   Writes back one cache line from the ARM7 data cache                            into memory.                                                           ______________________________________                                    

The Table A.2 lists ARM7 exceptions, which are detected and reported prior to executing the faulting instruction. The exception vector address is given in hexadecimal notation.

                  TABLE A.2                                                        ______________________________________                                         ARM7 Exceptions                                                                Exception Vector                                                                          Description                                                         ______________________________________                                         0x00000000 ARM7 Reset                                                          0x00000004 ARM7 Undefined Instruction Exception                                0x00000004 Vector Processor Unavailable Exception                              0x00000008 ARM7 Software Interrupt                                             0x0000000C ARM7 Single Step Exception                                          0x0000000C ARM7 Instruction Address Breakpoint Exception                       0x00000010 ARM7 Data Address Breakpoint Exception                              0x00000010 ARM7 Invalid Data Address Exception                                 0x00000018 ARM7 Protection Violation Exception                                 ______________________________________                                    

The follow describe the syntax of the extension to the ARM7 instruction ser. Refer to an ARM architecture document or the ARM7 Data Sheet (document number ARM DDI 0020C, issued Dec 1994) for a nomenclature description and the instruction formats.

The ARM architecture provides three instruction formats for coprocessor interface:

1. coprocessor data operations (CDP)

2. coprocessor data transfers (LDC, STC)

3. coprocessor register transfers (MRC, MCR)

The MSP architectural extensions use all three forms. The coprocessor data operations format (CDP) is used for the operations that need not communicate back to ARM7. ##STR1##

    ______________________________________                                         Field Meaning                                                                  ______________________________________                                         Cond  Condition field. This field specifies the condition in which the               instruction is to execute.                                               Opc   Coprocessor operation code.                                              CRn   Coprocessor operand register                                             CRd   Coprocessor destination register                                         CP#   Coprocessor number. The following coprocessor numbers are                      currently used:                                                                1111 - ARM7 data cache                                                         0111 - vector processor, extended registers                              CP    Coprocessor information.                                                 CPm   Coprocessor operand register.                                            ______________________________________                                    

The coprocessor data transfer format (LDC, STC) is used to load or store a subset of vector processor's registers directly to memory. The ARM7 processor is responsible for supplying the word address, and the vector processor supplies or accepts the data and controls the number of words transferred. Refer to the ARM7 Data Sheet for more detail. ##STR2## The fields in the format have the following conventions:

    ______________________________________                                         Field Meaning                                                                  ______________________________________                                         Cond  Condition field. This field specifies the condition in which the               instruction is to execute.                                               P     Pre/Post indexing bit.                                                   U     Up/Down bit.                                                             N     Transfer length. Due to not having enough bits in the CRd field,               the N bit is used as a part of source or destination register                  identifier.                                                              W     Write-back bit.                                                          L     Load/store bit.                                                          Rn    Base register.                                                           CRn   Coprocessor source/destination register.                                 CP#   Coprocessor number. The following coprocessor numbers are                      currently used:                                                                1111-ARM 7 data cache                                                          0111-vector processor, extended registers                                Offset                                                                               Unsigned 8 bit immediate offset.                                         ______________________________________                                    

The coprocessor register transfer format (MRC, MCR) is used communicate information directly between ARM7 and the vector processor. This format is used to move between an ARM7 register and a vector processor scalar or special-purpose register. ##STR3## The fields in the format have the following conventions:

    ______________________________________                                         Field  Meaning                                                                 ______________________________________                                         Cond   Condition field. This field specifies the condition in which the               instruction is to execute.                                              Opc    Coprocessor operation code.                                             L      Load/Store bit.                                                                L=0 means move to vector processor                                             L=1 means move from vector processor                                    CRn:Crm                                                                               Coprocessor source/destination register. Only                                  CRn<1:0>:CRm<3:0> are used.                                             Rd     ARM source/destination register                                         CP#    Coprocessor number. The following coprocessor numbers are                      currently used:                                                                1111 - ARM 7 data cache                                                        0111 - vector processor, extended registers                             CP     Coprocessor information.                                                ______________________________________                                    

Extended Arm Instruction Description

The extended ARM instructions are described in alphabetical order. ##STR4## Assembler Syntax

STC{cond} p15,cOpc, <Address>

CACHE{cond} Opc, <Address>

where cond={eq, he, cs, cc, mi, pl, vs, vc, hi, Is, ge, It, gt, le, ai, nv} and Opc={0, 1, 3}. Note that, since the CRn field of the LDC/STC format is used to specify the Opc, the decimal representation of the opcode must be preceded by the letter `c` (i.e., use cO instead of 0) in the first syntax. Refer to the ARM7 Data Sheet for the address mode syntax.

Description

This instruction is executed only if Cond is true. The Opc<3:0> specifies the following operations:

    ______________________________________                                         Opc<3:0>                                                                              Meaning                                                                 ______________________________________                                         0000   Writeback and invalidate the dirty cache line specified by the                 EA. If the matching line contains clean data, the line is                      invalidated without the writeback. If no cache line is found to                contain the EA, the data cache remains intact.                          0001   Writeback and invalidate the dirty cache line specified by the                 index of the EA. If the matching line contains clean data, the                 line is invalidated without the writeback.                              0010   Used by PFTCH and WBACK instructions.                                   0011   Invalidate the cache line specified by the EA. The cache line                  is invalidated (without writeback) even if the line is dirty).                 This is a privileged operation, and will cause ARM7                            Protection Violation if attempted in the user mode.                     others reserved.                                                               ______________________________________                                    

Operation

Refer to the ARM7 Data Sheet on how the EA is calculated.

Exception

ARM7 Protection Violation. ##STR5## Assembler Syntax

CDP{cond} p7, 1, c0, c0, co INTVP{cond}

where cond={eq, ne, cs, cc, mi, pl, vs, vc, hi, ls, ge, lt, gt, le, al, ns}.

Description

This instruction is executed only is Cond is true. This instruction signals the vector processor to halt. ARM 7 continues to execute the next instruction without waiting for the vector processor to halt.

A MFER busy-wait loop should be used to see if the vector processor has halted after this instruction is executed. This instruction has no affect if the vector processor is already in the VP₋₋ IDLE state.

Bits 19:12, 7:15 and 3:0 are reserved.

Exception

Vector processor unavailable. ##STR6## Assembler Syntax

MRC{cond} p7, 2, Rd, cP, cER, 0 MFER{cond} Rd, RNAME

where cond={eq, he, cs, cc, mi, pl, rs, vc, hi, ls, ge, lt, gt, le, al, nv}, Rd={rO,.r15}, P={0, 1 }, ER={0,. . 15} and RNAME refers to the architecturally specified register mnemonic (i.e., PERO or CSR).

Description

This instruction is executed only if Cond is true. The ARM7 register Rd is moved from the extended register ER specified with P:ER<3:0>, as shown in table below. Refer to Section 1.2 for extended register descriptions.

    ______________________________________                                         ER<3:0>         P = 0   P = 1                                                  ______________________________________                                         0000            UERO    PER0                                                   0001            UER1    PER1                                                   0010            UER2    PER2                                                   0011            UER3    PER3                                                   0100            UER4    PER4                                                   0101            UER5    PER5                                                   0110            UER6    PER6                                                   0111            UER7    PER7                                                   1000            UER8    PER8                                                   1001            UER9    PER9                                                   1010            UER10   PER10                                                  1011            UER11   PER11                                                  1100            UER12   PER12                                                  1101            UER13   PER13                                                  1110            UER14   PER14                                                  1111            UER15   PER15                                                  ______________________________________                                    

Exception

Protection violation when attempt to access PERx while in user mode. ##STR7## Assembler Syntax

MRC{cond} p7.1.Rd.Crn.CRm.0 MFVP{cond} Rd.RNAME

where cond={eq, ne, cs, cc, mi, pl, vs, vc, hi, ls, ge, lt, gt, le, al, nv}, Rd={r0, . . .r15}, CRn=({c0, . . . c15}, CRm={c0, . . . c15} and RNAME refers to the architecturally specified register mnemonic (i.e., SP0 or VCS).

Description

This instruction is executed only if Cond is true. The ARM7 register Rd is moved from the vector processor's scalar/special-purpose register CRn<1:0>:CRm<3:0>. Refer to Section 3.2.3 for vector processor register number assignment for register transfers.

Bits 7.5 as well as CRn<3:2> are reserved.

The vector processor register map is shown below.

Refer to Table 15 for the vector processor special-purpose registers (SP0-SP15).

    __________________________________________________________________________     CRM<3:0>                                                                              CRn<1:0>= 00                                                                           CRn<1:0>=01                                                                            CRn<1:0>=10                                                                            CRn<1:0>=111                                    __________________________________________________________________________     0000   SR0     SR16    SP0     RASR0                                           0001   SR1     SR17    SP0     RASR1                                           0010   SR2     SR18    SP0     RASR2                                           0011   SR3     SR19    SP0     RASR3                                           0100   SR4     SR20    SP0     RASR4                                           0101   SR5     SR21    SP0     RASR5                                           0110   SR6     SR22    SP0     RASR6                                           0111   SR7     SR23    SP0     RASR7                                           1000   SR8     SR24    SP0     RASR8                                           1001   SR9     SR25    SP0     RASR9                                           1010   SR10    SR26    SP0     RASR10                                          1011   SR11    SR27    SP0     RASR11                                          1100   SR12    SR28    SP0     RASR12                                          1101   SR13    SR29    SP0     RASR13                                          1110   SR14    SR30    SP0     RASR14                                          1111   SR15    SR31    SP0     RASR15                                          __________________________________________________________________________

SR0 always reads as 32 bits of zeros and a write to it is ignored.

Exception

Vector processor unavailable. ##STR8## Assembler Syntax

MRC{cond} p7, 2, Rd, cP, cER, 0 MFER{cond} Rd, RNAME

where cond={eq, he, cs, cc, mi, pl, rs, vc, hi, ls, ge, lt, gt, le, al, nv}, Rd={r0, . . r15}, P={0, 1 }, ER={0, . . 15} and RNAME refers to the architecturally specified register mnemonic (i.e., PERO or CSR).

Description

This instruction is executed only if Cond is true.

The ARM7 register Rd is moved from the extended register ER specified with P:ER<3:0>, as shown in table below.

    ______________________________________                                         ER<3:0>         P = 0   P = 1                                                  ______________________________________                                         0000            UERO    PER0                                                   0001            UER1    PER1                                                   0010            UER2    PER2                                                   0011            UER3    PER3                                                   0100            UER4    PER4                                                   0101            UER5    PER5                                                   0110            UER6    PER6                                                   0111            UER7    PER7                                                   1000            UER8    PER8                                                   1001            UER9    PER9                                                   1010            UER10   PER10                                                  1011            UER11   PER11                                                  1100            UER12   PER12                                                  1101            UER13   PER13                                                  1110            UER14   PER14                                                  1111            UER15   PER15                                                  ______________________________________                                    

Exception

Protection violation when attempt to access PERx while in user mode. ##STR9## Assembler Syntax

MRC{cond} p7.1.Rd.Crn.CRm.0 MFVP{cond} Rd.RNAME

where cond={eq, ne, cs, cc, mi, pl, vs, vc, hi, ls, ge, lt, gt, le, al, nv}, Rd={r0, . . . r15}, CRn=({c0, . . . c15}, CRm={c0, . . . c15} and RNAME refers to the architecturally specified register mnemonic (i.e., SP0 or VCS).

Description

This instruction is executed only if Cond is true. The ARM7 register Rd is moved from the vector processor's scalar/special-purpose register CRn<1:0>:CRm<3:0>.

Bits 7:5 as well as CRn<3:2> are reserved.

The vector processor register map is shown below.

    __________________________________________________________________________     CRM<3:0>                                                                              CRn<1:0>= 00                                                                           CRn<1:0>=01                                                                            CRn<1:0>=10                                                                            CRn<1:0>=111                                    __________________________________________________________________________     0000   SR0     SR16    SP0     RASR0                                           0001   SR1     SR17    SP0     RASR1                                           0010   SR2     SR18    SP0     RASR2                                           0011   SR3     SR19    SP0     RASR3                                           0100   SR4     SR20    SP0     RASR4                                           0101   SR5     SR21    SP0     RASR5                                           0110   SR6     SR22    SP0     RASR6                                           0111   SR7     SR23    SP0     RASR7                                           1000   SR8     SR24    SP0     RASR8                                           1001   SR9     SR25    SP0     RASR9                                           1010   SR10    SR26    SP0     RASR10                                          1011   SR11    SR27    SP0     RASR11                                          1100   SR12    SR28    SP0     RASR12                                          1101   SR13    SR29    SP0     RASR13                                          1110   SR14    SR30    SP0     RASR14                                          1111   SR15    SR31    SP0     RASR15                                          __________________________________________________________________________

Exception

Vector processor unavailable. t,430 ##STR10## Assembler Syntax

LDC{cond} p15, 2, <Address> PFTCH{cond} <Address>

where cond={eq, he, cs, cc, mi, pl, rs, vc, hi, Is, ge, lt, gt, le, al, nv }. Refer to the ARM7 Data Sheet for the address mode syntax.

Description

This instruction is executed only if Cond is true. The cache line specified by the EA is prefetched into the ARM7 data cache.

Operation

Refer to the ARM7 Data Sheet on how the EA is calculated.

Exception: None. ##STR11## Assembler Syntax

CDP{cond} p7, 0, cO, cO, cO STARTVP {cond}

where cond={eq, he, cs, cc, mi, pl, vs, vc, hi, Is, ge, it, gt, le, al, nv}.

Description

This instruction is executed only if Cond is true. This instruction signals the vector processor to start execution and automatically clears VISRC<vjp> and VISRC<vip>. ARM7 continues to execute the next instruction without waiting for the vector processor to start execution.

The vector processor's state must be initialized to the desired state before this instruction is executed. This instruction has no affect if the vector processor is already in the VP₋₋ RUN state.

Bits 19:12, 7:5 and 3:0 are reserved.

Exception

Vector processor unavailable. ##STR12## Assembler Syntax

MRC{cond} p7, 0, Rd, cO, cER, 0 TESTSET{cond} Rd, RNAME

where cond={eq, he, Cs, cc, mi, pl, rs, re, hi, ls, ge, It, gt, le, al, nv}, Rd={r0, . . r15}, ER={0, . . 15} and RNAME refers to the architecturally specified register mnemonic (i.e., UER1 or VASYNC).

Description

This instruction is executed only if Cond is true. This instruction returns the contents of UERX to RD and sets UERx<30> to 1. If the ARM7 register 15 is specified as the destination register, the UERx<30> is returned at the Z bit of CPSR such that a short busywait loop can be implemented.

Currently, only UER1 is defined to work with this instruction.

Bits 19:17 and 7:5 are reserved.

Exception: None

APPENDIX B

The architecture of multimedia processor 100 defines extended registers that processor 110 accesses with the MFER and MTER instructions. The extended registers include privileged extended registers and user extended registers.

The privileged extended registers are used mostly for controlling the operation of the Multimedia Signal Processor. They are shown in Table B.1.

                  TABLE B.1                                                        ______________________________________                                         Privileged extended registers                                                  Number                                                                               Mnemonic  Description                                                    ______________________________________                                         PER0  CTR       Control Register                                               PER1  PVR       Processor Version Register                                     PER2  VIMSK     Vector Interrupt Mask Register                                 PER3  AIABR     ARM7 Instruction Address Breakpoint Register                   PER4  ADABR     ARM7 Data Address Breakpoint Register                          PER5  SPREG     Scratch Pad Register                                           PER6  STR       Status Register                                                ______________________________________                                    

The Control Register controls the operation of the MSP 100. All bits in CTR are cleared upon reset. The register definition is shown in Table B.2.

                  TABLE B.2                                                        ______________________________________                                         CTR definition                                                                 Bit   Mnemonic  Description                                                    ______________________________________                                         31-13           reserved - always read as Os.                                  12    VDCI      Vector Data Cache Invalidate bit. When set,                                    causes the entire vector processor data cache                                  to become invalid. Since the cache                                             invalidation operation ususally conflicts with                                 normal cache operations, only one                                              invalidation code sequence is supported.                       11    VDE       Vector Data Cache Enable bit. When clear                                       disables the vector processor data cache.                      10    VICI      Vector Instruction Cache Invalidate bit.                                       When set, causes the entire vector processor                                   instruction cache to become invalid.                                           Since the cache invalidation operation                                         usually conflicts with normal cache                                            operations, only one invalidation code                                         sequence is supported.                                         9     VICE      Vector Instruction Cache Enable bit. When                                      clear disables the vector processor                                            instruction cache.                                             8     ADCI      ARM7 Data Cache Invalidate bit. When set,                                      causes the entire ARM7 data cache to become                                    invalid. Since the cache invalidation                                          operation usually conflicts with normal cache                                  operations, only one invalidation code                                         sequence is supported.                                         7     ADCE      ARM7 Data Cache Enable bit. When clear.                                        disables the ARM7 data cache.                                  6     AICI      ARM7 Instruction cache Invalidate bit. When                                    set, causes the entire ARM7 instruction cache                                  to become invalid. Since the cache                                             invalidation operation ususally conflicts with                                 normal cache operations, only one                                              invalidation code sequence is supported.                       5     AICI      ARM7 Instruction Cache Enable bit. When                                        clear, disables the ARM7 instruction cache.                    4     APSE      ARM7 Processor Single Step Enable bit. When                                    set, cause the ARM7 processor to take the                                      ARM7 Processor Single Step Exception after                                     executing one instruction. The single step                                     function is available only in the User or                                      Supervisor mode.                                               3     SPAE      Scratch Pad Access Enable bit. When set,                                       permits an ARM7 process to load from or store                                  to the scratch pad. When clear, a load or                                      store attempt to the scratch pad causes ARM7                                   Invalid Data Address exception.                                2     VPSE      Vector Processor Single Step Enable bit.                                       When set, cause the vector processor to take                                   the Vector Processor SIngle Step Exception                                     after executing one instruction.                               1     VPPE      Vector Processor Pipeline Enable bit. When                                     clear, configures the vector processor to                                      operate in a non-pipeline mode, in which                                       only one instruction is active in the vector                                   processor execution pipeline.                                  0     VPAE      Vector Processor Access Enable bit. When                                       set, permits an ARM7 process to execute the                                    extended ARM7 instructions, described above.                                   When clear, prevents a ARM7 process from                                       executing the extended ARM7 instructions.                                      Such an attempt causes Vector Processor                                        Unavailable exception.                                         ______________________________________                                    

The Status Register indicates the status of MSP 100. All bits in field STR are cleared upon reset. The register definition is shown in Table B.3.

                  TABLE B.3                                                        ______________________________________                                         STR definition                                                                 Bit   Mnemonic  Description                                                    ______________________________________                                         31:23           reserved - always read as Os                                   22    ADAB      ARM7 Data Address Breakpoint exception bit is                                  set when an ARM7 data address breakpoint                                       match occurs. This exception is reported                                       through Data Abort interrupt.                                  21    AIDA      ARM7 Invalid Data Address exception occurs                                     when an ARM7 load or store instruction tries                                   to access an address that is not defined or                                    implemented for a particular version of MSP                                    or when it tries to access the scratch pad                                     when not permitted. This exception is report                                   through Data Abort interrupt.                                  20    AIAB      ARM7 Instruction Address Breakpoint exception                                  bit is set when an ARM7 instruction address                                    breakpoint match occurs. This exception is                                     reported through Prefetch Abort interrupt.                     19    AIIA      ARM7 Invalid Instruction Address exception.                                    This exception is reported through Prefetch                                    Abort interrupt.                                               18    ASTP      ARM7 Single Step exception. This exception                                     is reported through Prefetch Abort interrupt.                  17    APV       ARM7 Protection Violation. This exception is                                   reported through IRQ interrupt.                                16    VPUA      Vector Processor Unavailable exception. This                                   exception is reported through Coprocessor                                      Unavailable interrupt.                                         15-0            reserved - always read as Os.                                  ______________________________________                                    

The Processor Version Register identifies the particular version of the particular processor of the Multimedia Signal Processor family of processors.

Vector Processor Interrupt Mask Register VIMSK controls reporting of vector processor exceptions to processor 110. Each bit in VIMSK, when set along with the corresponding bit in the VISRC register, enables the exception to interrupt the ARM7. It does not affect how the vector processor exception is detected but only affects whether the exception should interrupt the ARM7. All bits in VIMSK are clear upon reset. The register definition is shown in Table B.4.

                  TABLE B.4                                                        ______________________________________                                         VIMSK definition                                                               Bit     Mnemonic  Description                                                  ______________________________________                                         31      DABE      Data Address Breakpoint Interrupt Enable                     30      IABE      Instruction Address Breakpoint Interrupt                                       Enable                                                       29      SSTPE     Single Step Interrupt Enable                                 28-14             reserved - always read as Os.                                13      FOVE      Floating Point Overflow Interrupt Enable                     12      FINVE     Floating Point Invalid Operand Interrupt                                       Enable                                                       11      FDIVE     Floating Point Divide by Zero Interrupt                                        Enable                                                       10      IOVE      Integer Overflow Interrupt Enable                            9       IDIVE     Integer Divide by Zero Interrupt Enable                      8-7               reserved - always read as 0.                                 6       VIE       VCINT Interrupt Enable                                       5       VJE       VCJOIN Interrupt Enable                                      4-1               reserved - always read as 0.                                 0       CSE       Context Switch Enable                                        ______________________________________                                    

The ARM7 Instruction Address Breakpoint Register aids in debugging ARM7 programs. The register definition is shown in Table B.5.

                  TABLE B.5                                                        ______________________________________                                         AIABR definition                                                               Bit  Mnemonic  Description                                                     ______________________________________                                         31-2 IADR      ARM7 Instruction Address                                        1              reserved - always reads a 0.                                    0    IABE      Instruction Address Breakpoint Enable. Clear                                   upon reset. If set, causes the ARM7                                            Instruction Address Breakpoint exception to                                    occur when an ARM7 instruction access address                                  matches the AIABR<31:2> and VCSR<AIAB> is                                      clear. The VCSR<AIAB> is set to indicate the                                   exception. If VCSR<AIAB> is already set when                                   the match occurs, the VCSR<AIAB> is cleared                                    and a match is ignored. The exception is                                       reported before the instruction is executed.                    ______________________________________                                    

The ARM7 Data Address Breakpoint Register aids in debugging ARM7 programs. The register definition is shown in Table B.6.

                  TABLE B.6                                                        ______________________________________                                         ADABR definition                                                               Bit  Mnemonic  Description                                                     ______________________________________                                         31-2 DADR      ARM Data Address. Undefined upon reset.                         1    SABE      Store Address Breakpoint Enable. Clear upon                                    reset. If set, causes the ARM7 Data Address                                    Breakpoint exception to occur when the upper                                   30 bits of an ARM7 store access address                                        matches the ADABR<31:2> and VCSR<ADAB> is                                      clear. The VCSR<ADAB> is set to indicate the                                   exception. If VCSR<ADAB> is already set when                                   a match occurs, the VCSR<ADAB> is cleared and                                  the match is ignored. The exception is                                         reported before the store instruction is                                       executed.                                                       0    LABE      Load Address Breakpoint Enable. Clear upon                                     reset. If set, causes the ARM7 Data Address                                    Breakpoint exceptibn to occur when the upper                                   30 bits of an ARM7 load access address                                         matches the ADABR<31:2> and VCSR<ADAB> is                                      clear. The VCSR<ADAB> is set to indicate the                                   exception. If VCSR<ADAB> is already set when                                   a match occurs, VCSR<ADAB> is cleared and the                                  match is ignored. The exception is reported                                    before the load instruction is executed.                        ______________________________________                                    

The Scratch Pad Register configures the address and size of the scratch pad formed using SRAM in cache subsystem 130. The register definition is shown in Table B.7.

                  TABLE B.7                                                        ______________________________________                                         SPREG definition                                                               Bit   Mnemonic  Description                                                    ______________________________________                                         31-11 SPBASE    Scratch Pad Base indicates the upper 21 bit                                    of the starting address of the scratch pad.                                    This value must be the 4M byte offset from                                     the value in the MSP.sub.-- BASE register.                     10-2  reserved                                                                 1-0   SPSIZE    Scratch Pad Size.                                                              00->0K (with 4K vector processor data cache)                                   01->2K (with 2K vector processor data cache)                                   10->3K (with 1K vector processor data cache)                                   11->4K (with no vector processor data cache)                   ______________________________________                                    

The user extended registers are used mostly for synchronization of processors 110 and 120. The user extended registers are currently defined to have only one bit, mapped to bit 30, and instructions such as "MFER R15, UERx", for example, returns the bit value into the Z flag. The bits UERx<31> and UERx<29:0> are always read as zeros. The user extended registers are described in Table B.8.

                  TABLE B.8                                                        ______________________________________                                         User Extended Registers                                                        Number Mnemonic  Description                                                   ______________________________________                                         UER0   VPSTATE   Vector Processor State flag. Bit 30 when set                                   indicates that the vector processor is in                                      VP.sub.-- RUN state, executing instructions. If                                clear, indicates that the vector processor is                                  in VP.sub.-- IDLE state, and has halted with VPC                               addressing the next instruction to execute.                                    The VPSTATE<30> is clear upon reset.                          UER1   VASYNC    Vector and ARM7 synchronization flag. Bit 30                                   is provided for producer-consumer type of                                      synchronization between the vector and ARM7                                    processors 120 and 110. Vector processor 120                                   can set or cleared this flag using the VMOV                                    instruction. This flag can also be set or                                      cleared by an ARM7 process using a MFER or                                     MTER instruction. In addition, the flag can                                    be read and set using a TESTSET instruction.                  ______________________________________                                    

Table B.9 shows the extended registers' states upon a power-on reset.

                  TABLE B.9                                                        ______________________________________                                         Extended Register Power-on State                                               Register     Reset State                                                       ______________________________________                                         CTR          0                                                                 PVR          TBD                                                               VIMSK        0                                                                 AIABR        AIABR<0>=0, all others are undefined                              ADABR        ADABR<1:0>=0, all others are undefined                            STR          0                                                                 VPSTATE      VPSTATE<30>=0, all others are undefined                           VASYNC       VASYNC<30>=0, all others are undefined                            ______________________________________                                    

APPENDIX C

The architectural state of vector processor 120 includes: 32 32-bit scalar registers; 2 banks of 32 288-bit vector registers; a pair of 576-bit vector accumulator registers; a set of 32-bit special-purpose registers. The scalar, vector and accumulator registers are intended for general-purpose programming, and support many different data types.

The following notations are used in this and subsequent sections: VR indicates a vector register; VRi indicates the ith vector register (zero offset); VR i! indicates the ith data element in a vector register VR; VR<a:b> indicates bits a to b in a vector register VR; and VR i!<a:b> indicates bits a to b of the ith data element in a vector register VR.

A vector architecture has an added dimension of data types and sizes for the multiple elements within one vector register. Since a vector register is of a fixed size, the number of data elements it can hold depends on the size of the elements. The MSP architecture defines five element sizes as shown in Table C.1.

                  TABLE C.1                                                        ______________________________________                                         Data Element Sizes                                                             Size Name          Size Width (bits)                                           ______________________________________                                         Boolean            1                                                           Byte               8                                                           Byte9              9                                                           Halfword           16                                                          Word               32                                                          ______________________________________                                    

The MSP architecture interprets vector data according to the specified data type and size in an instruction. Currently, two's complement (integer) formats are supported for the byte, byte9, halfword and word element sizes on most arithmetic instructions. In addition, the IEEE 754 single precision format is supported with the word element size for most arithmetic instructions.

A programmer is free to interpret the data in any desired manner as long as the instruction sequence produces a meaningful result. For instance, the programmer is free to use the byte9 size to store 8-bit unsigned numbers and is equally free to store 8-bit unsigned numbers in the byte size data elements and operate on them using the provided two's complement arithmetic instructions, as long as the program can deal with "false" overflow results.

There are 32 scalar registers that are referred to as SR0 through SR31. The scalar registers are 32 bits wide and can contain one data element of any one of the defined sizes. Scalar register SR0 is special in that register SR0 always reads as 32 bits of zeros and a write to register SR0 is ignored. The byte, byte9 and halfword data types are stored in the least significant bits of scalar registers with the most significant bits having undefined values.

Since the registers do not have data type indicators, programmers must know the data type for the registers being used for each instruction. This is different from other architectures where a 32-bit register is assumed to contain a 32-bit value. The MSP architecture specifies that a result of a data type A correctly modify only the bits defined for the data type A. For instance, the result of a byte9 addition only modifies the lower 9-bits of the 32-bit destination scalar register. The values of the upper 23 bits are undefined unless stated otherwise for an instruction.

The 64 vector registers are organized into 2 banks, each with 32 registers. Bank 0 contains the first 32 registers and the bank 1 contains the second

32 registers. The two banks are used in a manner where one bank is set as the current bank and the other is set as the alternate bank. All vector instructions use the registers in the current bank by default, except the load/store and register move instructions which can access vector registers in the alternate bank. The CBANK bit in Vector Control and Status Register VCSR is used to set the bank 0 or bank 1 to be the current bank. (The other bank becomes the alternate banks.) The vector registers in the current bank are referred to as VR0 through VR31 and in the alternate bank are referred to as VRA0 through VRA31.

Alternatively, the two banks can be conceptually merged to provide 32 double-size vector registers of 576 bits each. The VEC64 bit in control register VCSR specifies this mode. In the VEC64 mode, there are no current and alternate banks, and a vector register number denotes a corresponding pair of 288-bit vector registers from the two banks. That is,

    VRi<575:0>=VR.sub.1 i<287:0>:VR.sub.0 i<287:0>

where VR₀ i and VR₁ i denote the vector registers having register number VRi in bank 1 and in bank 0, respectively. The double-size vector registers are referenced as VR0 through VR31.

The vector registers can accommodate multiple elements of the byte, byte9, halfword or word sizes as shown in Table C.2.

                  TABLE C.2                                                        ______________________________________                                         Number of Elements per Vector Register                                                                            Total                                                Element Length                                                                              Max Number of                                                                               Number of                                   Element Size                                                                            (bits)       Elements     Bits Used                                   ______________________________________                                         Byte9    9            32           288                                         Byte     8            32           256                                         Halfword 16           16           256                                         Word     32           8            256                                         ______________________________________                                    

Mixing of element sizes within one vector register is not supported. Except for the byte9 element size, only 256 of the 288 bits are used. In particular, every ninth bit is unused. The unused 32 bits in byte, halfword and word sizes are reserved, and programmers should not make any assumptions on their values.

The vector accumulator register is intended to provide storage for an intermediate result that has higher degree of precision than the result in a destination register. The vector accumulator register consists of four 288-bit registers, named VAC1H, VAC1L, VAC0H and VAC0L. The VAC0H:VAC0L pair is used by the three instructions by default. Only in VEC64 mode, the VAC1H:VAC1L pair is used to emulate the 64 byte9 vector operations. Even when the bank 1 is set to be the current bank in VEC32 mode, the VAC0H:VAC0L pair is used.

To produce an extended precision result with the same number of elements as in the source vector registers, extended precision elements are saved across a pair of registers, as shown in Table C.3.

                  TABLE C.3                                                        ______________________________________                                         Vector Accumulator Format                                                      Element                                                                        Size  Logical View                                                                              VAC Format                                                    ______________________________________                                         Byte9 VAC i!<17:0>                                                                              VAC0H i!<8>: VAC0L i!<8:0> for i=0 . . 31                                      and VAC1H i-32!<8:0>: VAC1L i-32!<8:0>                                         for i=32 . . 63                                               Byte  VAC i!<15:0>                                                                              VAC0H i!<7:0>: VAC0L i!<7:0> for                                               i=0 . . 31 and VAC1H i-32!<7:0>: VAC1L i-                                      32!<7:0> for i =32 . . 63                                     Half- VAC i!<31:0>                                                                              VAC0H i!<15:0>: VAC0L i!<15:0> for i=                         word             0 . . 15 and VAC1H i-16!<15:0>: VAC1L i-                                       16! i =16 . . 31                                              Word  VAC i!<63:0>                                                                              VAC0H i!<31:0>: VAC0L i!<31:0> for                                             i=0.7 and VAC1H i-8!<31:0>: VAC1L i-                                           8!<31:0> for i=8 . . 15                                       ______________________________________                                    

The VAC1H:VAC1L pair is used only in the VEC64 mode where the number of elements can be as many as 64, 32, or 16 for the Byte9 (and Byte), Halfword, and Word, respectively.

There are 33 special-purpose registers that and cannot be loaded directly from memory or stored directly to memory. Sixteen special-purpose registers, referred to as RASR0 to RASR15, form an internal return address stack and are used by the subroutine call and return instructions. Seventeen more 32-bit special-purpose registers are shown in Table C.4.

                  TABLE C.4                                                        ______________________________________                                         Special-purpose registers                                                      Number  Mnemonic  Description                                                  ______________________________________                                         SP0     VCSR      Vector Control and Status Register                           SP1     VPC       Vector Program Counter                                       SP2     VEPC      Vector Exception Program Counter                             SP3     VISRC     Vector Interrupt Source Register                             SP4     VIINS     Vector Interrupt Instruction Register                        SP5     VCR1      Vector Count Register 1                                      SP6     VCR2      Vector Count Register 2                                      SP7     VCR3      Vector Count Register 3                                      SP8     VGMR0     Vector Global Mask Register 0                                SP9     VGMR1     Vector Global Mask Register 1                                SP10    VOR0      Vector Overflow Register 0                                   SP11    VOR1      Vector Overflow Register 1                                   SP12    VIABR     Vector Instruction Address Breakpoint Reg.                   SP13    VDABR     Vector Data Address Breakpoint Register                      SP14    VMMR0     Vector Vector Move Mask Register 0                           SP15    VMMR1     Vector Vector Move Mask Register 1                           SP16    VASYNC    Vector & ARM7 Synchronization Register                       ______________________________________                                    

Vector control and status resister VCSR definition is shown in Table C.5.

                  TABLE C.5                                                        ______________________________________                                         VCSR definition                                                                Bit   Mnemonic  Description                                                    ______________________________________                                         31:18 reserved                                                                 17:13 VSP<4:0>  Return address stack pointer. VSP is used by                                   the jump to subroutine and return from                                         subrouting instructions to keep track of the                                   top of the internal return address stack.                                      There are only 16 entries in the return                                        address stack - VSP<4> is used for detecting                                   stack overflow condition.                                      12    SO        The summary overflow status flag. This bit                                     is set when an arithmetic operation results                                    in overflow. This bit is sticky - once set,                                    it remains set until cleared by writing 0 to                                   this bit.                                                      11    GT        The greater than status flag. This bit gets                                    set by the VSUBS instruction when SRa>SRb.                     10    EQ        The equal status flag. This bit gets set by                                    the VSUBS instruction when SRa=SRb.                            9     LT        The less than status flag. This bit gets set                                   by the VSUBS instruction when SRa<SRb.                         8     SMM       Select Move Mask. When this bit is set, the                                    VMMR0/1 pair becomes the element mask for the                                  arithmetic operations.                                         7     CEM       Complement Element Mask. When this bit is                                      set, the element mask is defined to be one's                                   whichever is configured to be the element                                      mask for arithmentic operation. This bit does                                  not change the contents of the VGMR0/1 or                                      VMMR0/1 - it only changes the use of these                                     registers. The SMM:CEM encodings specify:                                      00 - use VGMR0/1 as the element mask for all                                   but VCMOVM                                                                     01 - use ˜VGMR0/1 as the element mask for all                            but VCMOVM                                                                     10 - use VMMR0/1 as the element mask for all                                   but VCMOVM                                                                     11 - use ˜VMMR0/1 as the element mask for all                            but VCMOVM                                                     6     OED       Overflow Exception Disable. When this bit is                                   set, processor 120 continues with execution                                    upon detecting an overflow condition.                          5     ISAT      Integer saturation mode. The combination of                                    OED:ISAT bits specify:                                                         00 - no saturation of OED:ISAT bits specify:                                   00 - no saturation, report when overflow                                       exception occurs                                                               x1 - saturation, cannot cause overflow                                         10 - no saturation, do not report when                                         overflow exception occurs                                      4:3   RMODE     Rounding mode for IEEE 754 floating point                                      operations                                                                     00 round toward - infinity                                                     01 round toward zero                                                           10 round toward nearest                                                        11 round toward +infinity                                      2     FSAT      Floating point saturation (fast IEEE mode)                                     mode bit                                                       1     CBANK     Current Bank bit. When set indicates that                                      bank 1 is the current bank. When clear                                         indicates that bank 0 is the current bank.                                     CBANK is ignored when the VEC64 bit is set.                    0     VEC64     64 byte9 vector mode bit. When set specifies                                   that the vector registers and accumulators                                     are to have 576 bits. The default mode                                         specifies 32 of byte9 size, referred to as                                     the VEC32 mode.                                                ______________________________________                                    

Vector Program Counter Register VPC is the address of the next instruction to be executed by vector processor 120. ARM7 processor 110 should load register VPC before issuing the STARTVP instruction to start operation of vector processor 120

Vector Exception Program Counter VEPC specifics the address of the instruction that is most likely to have caused the most recent exception. MSP 100 does not support precise exceptions, hence the term "most likely".

Vector Interrupt Source Register VISRC indicates the interrupt sources to ARM7 processor 110. The appropriate bit(s) are set by hardware upon detection of exception(s). Software must clear register VISRC before vector processor 120 can resume execution. Any bit set in register VISRC causes vector processor 120 to enter state VP₋₋ IDLE. If the corresponding interrupt enable bit is set in VIMSK, an interrupt to processor 110 is signaled. Table C.6 defines the contents of register VISRC.

                  TABLE C.6                                                        ______________________________________                                         VISRC definition                                                               Bit  Mnemonic  Description                                                     ______________________________________                                         31   DAB       Data Address Breakpoint exception                               30   IAB       Instruction address breakpoint exception                        29   SSTP      Single Step exception                                           28-18          reserved                                                        17   IIA       Invalid Instruction Address exception                           16   IINS      Invalid Instruction exception                                   15   IDA       Invalid Data Address exception                                  14   UDA       Unaligned Data Access exception                                 13   FOV       Floating Point Overflow exception                               13   FINV      Floating Point Invalid Operand exception                        11   FDIV      Floating Point Divide by Zero exception                         10   IOV       Integer Overflow exception                                      9    IDIV      Integer Divide by Zero exception                                48   RASO      Return Address Stack Overflow exception                         7    RASU      Return address Stack Underflow exception                        6    VIP       VCINT exception pending. Executing STARTVP                                     instruction clears this bit.                                    5    VJP       VCJOIN exception pending. Executing STARTVP                                    instruction clears this bit.                                    4-0  VPEV      Vector Processor Exception Vector.                              ______________________________________                                    

Vector Interrupt Instruction Register VIINS is updated with the VCINT or VCJOIN instruction when the VCINT or VCJOIN instruction is executed to interrupt ARM7 processor 110.

Vector Count Registers VCR1, VCR2, and VCR3 are for Decrement And Branch instruction VD1CBR, VD2CBR, and VD3CBR and are initialized with counts of loops to be executed. When instruction VD1CBR is executed, register VCR1 is decremented by 1. If the count value is not zero and the condition specified in the instruction matches the VFLAG, then the branch is taken. If not, the branch is not taken. Register VCR1 is decremented by 1 in either case. Registers VCR2 and VCR3 are used in the same fashion.

Vector Global Mask Reqister VGMR0 indicates the elements of the destination vector register that are to be affected in the VEC32 mode and the elements within VR<287:0> in the VEC64 mode. Each bit in VGMR0 controls the update of 9 bits in the vector destination register. Specifically, VGMR0<i> controls the update of VRd<9i+8:9i> in the VEC32 mode and of VR₀ d<9i+8:9i> in the VEC64 mode. Note that VR_(o) d denotes the destination register in bank 0 in the VEC64 mode and that VRd refers to the destination register in the current bank, which can either be the bank 0 or bank 1, in the VEC32 mode. Vector global mask register VGMR0 is used in execution of all instructions except the VCMOVM instruction.

Vector Global Mask Register VGMR1 indicates the elements within VR<575:288> that are affected in the VEC64 mode. Each bit in register VGMR1 controls the update of 9 bits in the vector destination register in bank 1. Specifically, VGMR1<i> controls the update of VR₁ d<9i+8:9i>. Register VGMR1 is not used in the VEC32 mode but, in VEC64 mode, affects execution all instructions except the VCMOVM instruction.

Vector Overflow Register VOR0 indicates the elements in the VEC32 mode and the elements within VR<287:0> in the VEC64 mode that contain overflow results after a vector arithmetic operation. This register is not modified by a scalar arithmetic operation. Bit VOR0<i> being set indicates that the ith element of the byte or byte9, the (i idiv 2)th element of the halfword, or the (i idiv 4)th element of the word data type operation contains an overflow result. For instance, bit 1 and bit 3 would be set to indicate overflow of the first halfword and word element, respectively. This mapping of bits in VOR0 is different from the mapping of the bits in VGMR0 or VGMR1.

Vector Overflow Resister VOR1 is used to indicate the elements within VR<575:288> in the VEC64 mode that contains overflow results after a vector arithmetic operation. Register VOR1 is not used in the VEC32 mode nor modified by a scalar arithmetic operation. Bit VOR1<i> being set indicates that the ith element of the byte or byte9, the (i idiv 2)th element of the halfword, or the (i idiv 4)th element of the word data type operation contains an overflow result. For instance, bit 1 and bit 3 would be set to indicate overflow of the first halfword and word element, respectively in VR<575:288>. The mapping of bits in VOR1 is different from the mapping of the bits in VGMR0 or VGMR1.

Vector Instruction Address Breakpoint Register VIABR aids in debugging vector programs. The register definition is shown in Table C.7.

                  TABLE C.7                                                        ______________________________________                                         VIABR defination                                                               Bit  Mnemonic  Description                                                     ______________________________________                                         31-2 IADR      Vector Instruction Address. Undefined upon reset.               1              reserved                                                        0    IABE      Instruction Address Breakpoint Enable. Undefined                               upon reset. If set, causes the Vector Instruction                              Address Breakpoint exception to occur when a                                   vector instruction access address matches the                                  VIABR<31:2>. Bit VISRC<IAB> is set to indicate                                 the exception. The exception is reported before the                            instruction is executed.                                        ______________________________________                                    

Vector Data Address Breakpoint Register VDABR aids in debugging vector programs. The register definition is shown in Table C.8.

                  TABLE C.8                                                        ______________________________________                                         VDABR defination                                                               Bit  Mnemonic  Description                                                     ______________________________________                                         31-2 DADR      Vector Data Address. Undefined upon reset.                      1    SABE      Store Address Breakpoint Enable. Undefined upon                                reset. If set, causes the Vector Data Address                                  Breakpoint exception to occur when a vector store                              access address matches the VDABR<31:2>. Bit                                    VISRC<DAB> is set to indicate the exception. The                               exception is reported before the store instruction is                          executed.                                                       0    LABE      Load Address Breakpoint Enable. Clear upon reset.                              If set, causes the Vector Data Address Breakpoint                              exception to occur when a vector load access                                   matches the VDABR<31:2>. The VISRC<DAB>is                                      set to indicate the exception. The exception is                                reported before the load instruction is executed.               ______________________________________                                    

Vector Move Mask Register VMMR0 is used by the VCMOVM instruction at all times as well as when VCSR<SMM>=1 for all instructions. Register VMMR0 indicates the elements of the destination vector register that are to be affected in the VEC32 mode and the elements within VR<287:0> in the VEC64 mode. Each bit in VMMR0 controls the update of 9 bits in the vector destination register. Specifically, VMMR0<i> controls the update of VRd<9i+8:9i>in the VEC32 mode and of VR_(o) d<9i+8:9i>in the VEC64 mode. VR0d denotes the destination register in bank 0 in the VEC64 mode and that VRd refers to the destination register in the current bank, which can either be the bank 0 or bank 1. in the VEC32 mode.

Vector Move Mask Register VMMR1 is used by the VCMOVM instruction at all times as well as when VCSR<SMM>=1 for all instructions. Register VMMR1 indicates the elements within VR<575:288> that are to be affected in the VEC64 mode. Each bit in VMMR1 controls the update of 9 bits in the vector destination register in bank 1. Specifically, VGMR1<i> controls the update of VR1d<9i+8:9i>. Register VGMR1 is not used in the VEC32 mode.

Vector and ARM7 Synchronization Register VASYNC provides producer/consumer type of synchronization between processes 110 and 120. Currently, only bit 30 is defined. An ARM7 process can access register VASYNC using instructions MFER, MTER, and TESTSET while vector processor 120 is in state VP₋₋ RUN or state VP₋₋ IDLE. Register VASYNC is not accessible to an ARM7 process through TVP or MFVP instructions since these instructions cannot access beyond the first 16 vector processor's special purpose registers. A vector process can access register VASYNC through a VMOV instruction.

Table C.9 shows the vector processor's state upon a power-on reset.

                  TABLE C.9                                                        ______________________________________                                         Vector Processor Power-on Reset State                                                 Register     Reset State                                                ______________________________________                                                SR0          0                                                                 all others   undefined                                                  ______________________________________                                    

The special-purpose registers are initialized by ARM7 processor 110 before the vector processor can execute an instruction.

APPENDIX D

Each instruction either implies or specifies the data type of the source and destination operands. Some instructions have semantics that apply equally to more than one data type. Some instructions have semantics that take one data type for the source and produce a different data type for the result. This appendix describes the data types supported by the exemplary embodiment. Table 1 in the application describes the data types int8, int9, int16, int32 and float which are supported. Unsigned integer formats are not supported and that an unsigned integer value must first be converted to a 2's complement format before being used. The programmer is free to use arithmetic instructions with unsigned integer or any other formats of his choice as long as overflows are handled properly. The architecture defines overflows of only 2's complement integer and 32-bit floating point data types. The architecture does not detect carry out of 8, 9, 16 or 32-bit operations that is necessary to detect unsigned overflows.

Table D.1 shows the data sizes supported by the load operations.

                  TABLE D.1                                                        ______________________________________                                         Data Sizes Supported by Load Operations                                        Data Size                                                                              Data Size                                                              in Memory                                                                              in Register                                                                             Load Operation                                                ______________________________________                                          8-bit   9-bit   load 8-bits, sign-extend to 9-bits (for loading                                8-bit two's complement)                                        8-bit   9-bit   load 8-bits. zero-extend to 9-bits (for loading                                8-bit unsigned)                                               16-bit  16-bit   load 16-bits (for loading 16-bit unsigned or                                   two's complement)                                             32-bit  32-bit   load 32-bits (for loading 32-bit unsigned, two's                               complement integer or 32-bit floating point)                  ______________________________________                                    

The architecture specifies the memory address alignment to be on data type boundaries. That is, for a byte there is no alignment requirement. For a halfword, the alignment requirement is halfword boundary. For a word, the alignment requirement is word boundary.

Table D.2 shows the data sizes supported by the store operations.

                  TABLE D.2                                                        ______________________________________                                         Data Sizes Supported by Store Operations                                       Data Size                                                                             Data Size                                                               in Register                                                                           in Memory Store Operation                                               ______________________________________                                          8-bit  8-bit    store 8-bits (stores 8-bit unsigned or two's                                   complement)                                                    9-bit  8-bit    truncate to lower 8-bits, store 8-bits (stores                                 9-bit two's complement having value between                                    0 and 255 - unsigned)                                         16-bit 16-bit    store 16-bits (store 16-bit unsigned or two's                                  complement)                                                   32-bit 32-bit    store 32-bits                                                 ______________________________________                                    

Since more than one dam type is mapped to a register, be it scalar or vector, there may be bits in the destination register that have no defined result for some data types. In fact, other than for the byte9 data size operation on a vector destination register and for the word data size operation on a scalar destination register, there are bits in a destination register whose values are not defined by the operation. For these bits, the architecture specifies that their values be undefined. Table D.3 shows the bits that are undefined for each data size.

                  TABLE D.3                                                        ______________________________________                                         Undefined Bits for the Data Sizes                                                         Vector Destination                                                                              Scaler Destination                                 Data Size  Register         Register                                           ______________________________________                                         byte       VR<9i+8>, for i=0 to 31                                                                         SR<31:8>                                           byte9      none             SR<31:9>                                           halfword   VR<9i+8>, for i=0 to 31                                                                         SR<31:16>                                          word       VR<9i+8>, for i=0 to 31                                                                         none                                               ______________________________________                                    

Programmers must be aware of the data types of the source and destination registers or memory when programming. A data type conversion from one element size to another potentially results in different number of elements being stored in a vector register. For instance, the conversion of a vector register from the halfword to the word data type requires two vector registers to store the same number of converted elements. Conversely, a conversion from the word data type, which may have a user-defined format in the vector register, to the halfword format produces the same number of elements in one-half of a vector register and the residual bits in the other half. In either cases, data type conversions create an architectural issue with the arrangement of the converted elements that are of different size from the source elements.

As a principle, the MSP architecture does not provide operations that implicitly change the number of elements as the result. The architecture views that the programmer must be aware of the consequences of changing the number of elements in the destination register. The architecture only provides operations that convert from one data type to another data type of the same size, and requires the programmer to adjust for the differences in data sizes when converting from one data type to another of different size.

Special instructions such as VSHFLL and VUNSHFLL as described in Appendix E simplify the conversion of a vector having a first data size to a second vector having a second data size. The basic steps involved in converting two's complement data type from a smaller element size, int8 for instance, in vector VR_(a) to a larger size, int16 for instance, are:

1. Shuffle the elements in VR_(a) with another vector VR_(b) into two vectors VR_(c) :VR_(d) using the byte data type. The elements in VR_(a) are moved to the lower bytes of int16 data elements in a double-size register VR_(c) :VR_(d), and the elements of VR_(b), whose values are irrelevant, are moved to the upper bytes of VR_(c) :VR_(d). This operation effectively moves one half of the elements of VR_(a) into VR_(c) and the other half into VR_(d) while doubling the size of each element from byte to halfword.

2. Arithmetic shift the elements in VRc:VRd by 8 bits to sign-extend them.

The basic steps involved in converting two's complement data type from a larger element size, int16 for instance, in vector VR_(a) to a smaller size, int8 for instance, are:

1. Check to ensure that the each element in the int16 data type are representable in the byte size. If necessary, saturate the elements at both ends to fit in the smaller size.

2. Unshuffle the elements in VR_(a) with another vector VR_(b) into two vectors VR_(c) :VR_(d). The upper halves of each element in VR_(a) and VR_(b) are moved to VR_(c) and the lower halves are moved to VR_(d). This effectively collects the lower halves of all elements in VR_(a) in the lower half of VR_(d).

Special instructions are provided for the following data type conversions: int32 to single precision floating point; single precision floating point to fixed point (X.Y notation); single precision floating point to int32; int8 to int9; int9 to int16; and int16 to int9.

To provide flexibility in vector programming, most vector instructions use an element mask to operate only on the selected elements within a vector. The Vector Global Mask Registers VGMR0 and VGMR1 identify the elements that are modified in the destination register and the vector accumulator by the vector instructions. For byte and byte9 data size operations, each of the 32 bits in the VGMR0 (or VGMR1) identifies an element to be operated on. Bit VGMR0<i> being set indicates that the element i of byte size is to be affected, i being 0 to 31. For halfword data size operations, each pair of the 32 bits in VGMR0 (or VGMR1) identifies an element to be operated on. Bits VGMR0<2i:2i+1> being set indicates that the element i is to be affected, i being 0 to 15. If only one bit of a pair in VGMR0 is set for an halfword data size operation, only the bits in the corresponding byte are modified. For word data size operations, each set of four bits in VGMR0 (or VGMR1) identifies an element to be operated on. Bits VGMR0<4i:4i+3> being set indicates that the element i is to be affected, i being 0 to 7. If not all bits in a set of four in VGMR0 are set for a word data size operation, only the bits in the corresponding byte are modified.

The VGMR0 and VGMR1 can be set by comparing a vector register with a vector or scalar register or with an immediate value using the VCMPV instruction. This instruction properly sets the mask according to the specified data size. Since a scalar register is defined to contain only one data element, the scalar operations (that is, the destination registers are scalar) are not affected by the element mask.

For flexibility in vector programming, most MSP instructions support three forms of vector and scalar operations. They are:

1. vector=vector op vector

2. vector=vector op scalar

3. scalar=scalar op scalar

For the case 2 where a scalar register is specified as the B operand, the single element in the scalar register is replicated as many as needed to match the number of elements within the vector A operand. The replicated elements are of the same value as the element in the specified scalar operand. The scalar operand can be from a scalar register or from the instruction, in the form of immediate operand. In case of an immediate operand, the appropriate sign-extension is applied if the specified data type uses a larger data size than available with the immediate field size.

In many multimedia applications, special attention must be paid to the precision of the source, intermediate and final result. In addition, the integer multiply instructions produce "double precision" intermediate results that can be stored in two vector registers.

The MSP architecture currently supports two's complement integer formats for 8, 9, 16 and 32-bit elements and the IEEE 754 single precision format for 32-bit elements. An overflow is defined to be a result that is beyond the most positive or the most negative value representable by the specified data type. When an overflow occurs, the value written to the destination register is not a valid number. An underflow is defined only for the floating point operations.

Unless state otherwise, all floating point operations use one of the four rounding modes specified in bits VCSR<RMODE>. Some instructions use what is known as round away from zero (round even) rounding mode. These instructions are explicitly stated.

Saturation is an important function in many multimedia applications. The MSP architecture supports saturation in all four integer and the floating point operations. bit ISAT in register VCSR specifies the integer saturation mode. The floating point saturation mode, which is also known as fast IEEE mode, is specified with FSAT bit in the VCSR. When saturation mode is enabled, a result that is beyond the most positive or the most negative values is set to the most positive or the most negative values, respectively. An overflow cannot occur in this case, and an overflow bit cannot be set.

Table D.4 lists precise exceptions, which are detected and reported prior to executing the faulting instruction. The exception vector address is given in hexadecimal notation.

                  TABLE D.4                                                        ______________________________________                                         Precise Exceptions                                                             Exception                                                                      Vector  Description                                                            ______________________________________                                         0x00000018                                                                             Vector Processor Instruction Address Breakpoint Exception              0x00000018                                                                             Vector Processor Data Address Breakpoint Exception                     0x00000018                                                                             Vector Processor Invalid Instruction Exception                         0x00000018                                                                             Vector Processor Single Step Exception                                 0x00000018                                                                             Vector Processor Return Address Stack Overflow Exception               0x00000018                                                                             Vector Processor Return Address Stack Underflow                                Exception                                                              0x00000018                                                                             Vector Processor VCINT Exception                                       0x00000018                                                                             Vector Processor VCJOIN Exception                                      ______________________________________                                    

Table D.5 lists imprecise exceptions, which are detected and reported after executing some number of instruction that are later in program order than the faulting instruction.

                  TABLE D.5                                                        ______________________________________                                         Imprecise Exceptions                                                           Exception                                                                      Vector  Description                                                            ______________________________________                                         0x00000018                                                                             Vector Processor Invalid Instruction Address Exception                 0x00000018                                                                             Vector Processor Invalid Data Address Exception                        0x00000018                                                                             Vector Processor Unaligned Data Access Exception                       0x00000018                                                                             Vector Processor Integer Overflow Exception                            0x00000018                                                                             Vector Processor Floating Point Overflow Exception                     0x00000018                                                                             Vector Processor Floating Point Invalid Operand Exception              0x00000018                                                                             Vector Processor Floating Point Divide by Zero Exception               0x00000018                                                                             Vector Processor Integer Divide by Zero Exception                      ______________________________________                                    

APPENDIX E

The instruction set for vector processor includes eleven classification as shown in Table E.1.

                  TABLE E.1                                                        ______________________________________                                         Vector instruction class summary                                               Class     Description                                                          ______________________________________                                         Control Flow                                                                             This class includes the instructions that control the                          program flow including branch and ARM7 interface                               instructions.                                                        Logical (bit-                                                                            This class includes the bit-wise logical instructions.               wise, mask)                                                                              Although the (bit-wise, mask) data type is Boolean, the                        Logical instructions use the element mask to modify                            the results, and therefore requires data type.                       Shift & Rotate                                                                           This class includes the instructions that shift and                  (element-wise,                                                                           rotate the bits mask) within each element. This class                mask)     differentiates the element sizes, and is affected by the                       element mask.                                                        Arithmetic                                                                               This class includes the element-wise arithmetic                      (element-wise,                                                                           instructions. That (element-wise, mask) is, the result of            mask)     ith element is computed from the ith elements of the                           sources. This class differentiates the element types,                          and is affected by the element mask.                                 Multimedia                                                                               This class includes instructions that are optimized for              (element wise-                                                                           multimedia (element-wise, mask) applications. This                   mask)     class differentiates the element types, and is affected                        by the element mask.                                                 Data Type This class includes instructions that convert elements               Conversion                                                                               from one (element-wise, no mask) data type to                        (element-wise,                                                                           another. Instructions in this class support a specific               no mask)  set of data types, and are not subject to the element                          mask since the architecture does not support having                            more than one data type in a register.                               Inter-element                                                                            This class includes instructions that take two                       Arithmetic                                                                               elements from different positions in the vectors to                            produce arithmetic results.                                          Inter-element                                                                            This class includes instructions that take two elements              Move      from different positions in the vectors to rearrange the                       elements.                                                            Load/Store                                                                               This class includes instructions that load or store                            registers. These instructions are not affected by the                          element mask.                                                        Cache Operation                                                                          This class includes instructions that control instruction                      and data caches. These instructions are not affected by                        the element mask.                                                    Register Move                                                                            This class includes instructions that transfer data                            between two registers. These instructions are normally                         not affected by the element mask, but some have the                            option to use the element mask.                                      ______________________________________                                    

Table E.2 lists the flow control instructions.

                  TABLE E.2                                                        ______________________________________                                         Flow Control Instructions                                                      Mnemonic     Description                                                       ______________________________________                                         VCBR         Conditional Branch                                                VCBRI        Conditional Branch Indirect                                       VDICBR       Decrement VCR1 and Conditional Branch                             VD2CBR       Decrement VCR2 and Conditional Branch                             VD3CBR       Decrement VCR3 and Conditional Branch                             VCJSR        Conditional Jump to Subroutine                                    VCJSRI       Conditional Jump to Subroutine Indirect                           VCRSR        Conditional Return from Subroutine                                VCINT        Conditional Interrupt ARM7                                        VCJOIN       Conditional Join With ARM7                                        VCCS         Condtional Context Switch                                         VCBARR       Conditional Barrier                                               VCHGCR       Change Control Register (VCSR)                                    ______________________________________                                    

The logical class supports the Boolean data types, and are affected by the element mask. Table E.3 lists the flow control instructions.

                  TABLE E.3                                                        ______________________________________                                         Logic Instructions                                                             Mnemonic        Description                                                    ______________________________________                                         VNOT            NOT - ˜ B                                                VAND            AND - (A & B)                                                  VCAND           Complement AND - (-A & B)                                      VANDC           AND Complement - (A & -B)                                      VNAND           NAND - ˜ (A & B)                                         VOR             OR - (A | B )                                         VCOR            Complement OR - (˜A | B)                        VORC            OR Complement - (A | ˜B)                        VNOR            NOR - ˜ (A | B)                                 VXOR            Exclusive OR - (A   B)                                         VXNOR           Exclusive NOR - ˜ (A   B)                                ______________________________________                                    

The shift/rotate class instructions operate on the int8, int9, int16 and int32 data types (no float data type), and are affected by the element mask. Table E.4 lists the Shift/rotate class instructions.

                  TABLE E.4                                                        ______________________________________                                         Shift & Rotate class                                                           Mnemonic          Description                                                  ______________________________________                                         VDIV2N            Divide by Power of 2                                         VLSL              Logical Shift Left                                           VLSR              Logical Shift Right                                          VROL              Rotate Left                                                  VROR              Rotate Right                                                 ______________________________________                                    

The arithmetic class instructions, in general, support the int8, int9, int16, int32, and float data types, and are affected by the element mask. For specific limitations on unsupported data types, refer to detail description of each instruction below. The VCMPV instruction is not affected by the element mask, since it operates on element mask. Table E.5 lists the arithmetic class instructions.

                  TABLE E.5                                                        ______________________________________                                         Arithmetic Class                                                               Mnemonic  Description                                                          ______________________________________                                         VASR      Arithmetic Shift Right                                               VADD      Add                                                                  VAVG      Average                                                              VSUB      Subtract                                                             VASUB     Absolute of Subtract                                                 VMUL      Multiply                                                             VMULA     Multiply to Accumulator                                              VMULAF    Multiply to Accumulator Fraction                                     VMULF     Multiply Fraction                                                    VMULFR    Multiply Fraction and Round                                          VMULL     Multiply Low                                                         VMAD      Multiply and Add                                                     VMADL     Multiply and Add Low                                                 VADAC     Add and Accumulate                                                   VADACL    Add and Accumulate Low                                               VMAC      Multiply and Accumulate                                              VMACF     Multiply and Accumulate Fraction                                     VMACL     Multiply and Accumulate Low                                          VMAS      Multiply and Subtract from Accumulator                               VMASF     Multiply and Subtract from Accumulator Fraction                      VMASL     Multiply and Subtract from Accumulator Low                           VSATU     Saturate To Upper Limit                                              VSATL     Saturate to Lower Limit                                              VSUBS     Subtract Scalar and Set Condition                                    VCMPV     Compare Vector and Set Mask                                          VDIVI     Divide Initialize                                                    VDIVS     Divide Step                                                          VASL      Arithmetic Shift Left                                                VASA      Arithmetic Shift Accumulator by 1 bit                                ______________________________________                                    

The MPEG instructions are a class of instructions specially suited for MPEG encoding and decoding, but can be used in a variety of manners. The MPEG instructions support the int8, int9, int16 and int32 data types, and are affected by the element mask. Table E.6 lists the MPEG instructions.

                  TABLE E.6                                                        ______________________________________                                         MPEG class                                                                     Mnemonic    Description                                                        ______________________________________                                         VAAS3       Add and Add Sign of (-1, 0, 1)                                     VAAS3       Add and Subtract Sign of (-1, 0, 1)                                VEXTSGN2    Extract Sign of (-1, 1)                                            VEXTSGN3    Extract Sign of (-1, 0, 1)                                         VXORALL     XOR the least-significant-bit of all elements                      ______________________________________                                    

Each data type conversion instruction supports specific data types, and is not affected by the element mask since the architecture does not support more than one data type in a register. Table E.7 list the data type conversion instructions.

                  TABLE E.7                                                        ______________________________________                                         Data Type Conversion Class                                                     Mnemonic                                                                               Description                                                            ______________________________________                                         VCVTIF  Convert Integer to Floating point                                      VCVTFF  Convert Floating Point to Fixed Point                                  VROUND  Round Floating Point to Integer (supports 4 IEEE rounding                      modes)                                                                 VCNTLZ  Count Leading Zeroes                                                   VCVTB9  Convert Byte9 Data Type                                                ______________________________________                                    

The inter-element arithmetic class of instructions support the int8, int9, int16, int32 and float data types. Table E.8 lists instructions in the inter-element arithmetic class.

                  TABLE E.8                                                        ______________________________________                                         Inter-element Arithmetic Class                                                 Mnemonic    Description                                                        ______________________________________                                         VADDH       Add Two Adjacent Elements                                          VAVGH       Average Two Adjacent Elements                                      VAVGQ       Average Quad Elements                                              VMAXE       Maximum Exchange Even/Odd Elements                                 ______________________________________                                    

The inter-element move class of instructions support byte, byte9, halfword and word data sizes. Table E.9 lists the inter-element move class of instructions.

                  TABLE E.9                                                        ______________________________________                                         Inter-element Move Class                                                       Mnemonic     Description                                                       ______________________________________                                         VESL         Element Shift Left by 1                                           VESR         Element Shift Right by 1                                          VSHFL        Shuffle to Even/Odd Elements                                      VSHFL        Shuffle to Even/Odd Elements                                      VSHFLH       Shuffle to Even/Odd Elements High                                 VSHFLL       Shuffle to Even/Odd Elements Low                                  VUNSHFL      Unshuffle to Even/Odd Elements                                    VUNSHFLH     Unshuffle to Even/Odd Elements High                               VUNSHFLL     Unshuffle to Even/Odd Elements Low                                ______________________________________                                    

The load/store instructions support, in addition to byte, halfword, and word data sizes, special byte9 related data size operations, and are not affected by the element mask. Table E.10 lists instructions in the load/store class.

                  TABLE E.10                                                       ______________________________________                                         Load/Store Class                                                               Mnemonic        Description                                                    ______________________________________                                         VL              Load                                                           VLD             Load Double                                                    VLQ             Load Quad                                                      VLCB            Load From Circular Buffer                                      VLR             Load Reverse Element Order                                     VLWS            Load With Stride                                               VST             Store                                                          VSTD            Store Double                                                   VSTQ            Store Quad                                                     VSTCB           Store to Circular Buffer                                       VSTR            Store Reverse Element Order                                    VSTWS           Store With Stride                                              ______________________________________                                    

The most register move instructions support the int8, int9, int16, int32 and float data types, and are not affected by the element mask. Only the VCMOVM instruction is affected by the element mask. Table E.11 lists the register move class of instructions.

                  TABLE E.11                                                       ______________________________________                                         Register Move Class                                                            Mnemonic     Description                                                       ______________________________________                                         VLI          Load Immediate                                                    VMOV         Move                                                              VCMOV        Conditional Move                                                  VCMOVM       Conditional Move with Element Mask                                VEXTRT       Extract An Element                                                VINSERT      Insert An Element                                                 ______________________________________                                    

Table E.12 list instructions in the Cache Operation Class which control cache subsystem 130.

                  TABLE E.12                                                       ______________________________________                                         Cache Operation Class                                                          Mnemonic    Description                                                        ______________________________________                                         VCACHE      Cache operation to data or instruction cache                       VPFTCH      Prefetch into data cache                                           VWBACK      Writeback from data cache                                          ______________________________________                                    

Instruction Description Nomenclature

To simplify the specification of the instruction set, special terminology is used throughout the appendices. For example, instruction operands are signed two's-complement integers of byte, byte9, halfword or word sizes, unless otherwise noted. The term "register" is used to denote a general-purpose (scalar or vector) register. Other types of registers are described explicitly. In the assembly-language syntax, suffixes b, b9, h and w denote both the data sizes (byte, byte9, halfword, and word) and the integer data types(int8, int9, int16 and int32). Further, terminology and symbols used to describe instruction operands, operations, and the assembly-language syntax are as follows.

    ______________________________________                                         Rd        destination register (vector, scalar or                                        special-purpose)                                                     Ra, Rb    source registers a and b (vector, scalar or                                    special-purpose)                                                     Rc        source or destination register c (vector or                                    scalar)                                                              Rs        store data source register (vector or scalar)                        S         32-bit scalar or special-purpose register                            VR        current bank vector register                                         VRA       alternate bank vector register                                       VR.sub.0  bank 0 vector register                                               VR.sub.1  bank 1 vector register                                               VRd       vector destination register (default to                                        current bank unless VRA is specified).                               VRa, VRb  vector source registers a and b                                      VRc       vector source or destination register c                              VRs       vector store data source register                                    VAC0H     Vector Accumulator Register 0 High                                   VAC0L     Vector Accumulator Register 0 Low                                    VAC1H     Vector Accumulator Register 1 High                                   VAC1L     Vector Accumulator Register 1 Low                                    SRd       scalar destination register                                          SRa, SRb  scalar source registers a and b                                      SRb+      update the base register with the effective                                    address                                                              SRs       scalar store data source register                                    SP        special-purpose register                                             VR i!     ith element in vector register VR                                    VR i!<a:b>                                                                               bits a to b of the ith element in vector                                       register VR                                                          VR i!<msb>                                                                               the most-significant-bit of the ith                                            element in vector register VR                                        EA        effective address for memory access                                  MEM       memory                                                               BYTE EA!  one byte in memory addressed by EA                                   HALF EA!  the halfword in memory addressed by EA. Bits                                   <15:8> are addressed by EA+1.                                        WORD EA!  a word in memory addressed by EA. Bits                                         <31:24> are addressed by EA+3.                                       NumElem   denotes the number of elements for a given                                     data type. It is 32, 16 or 8 for byte and                                      byte9, halfword, or word data sizes,                                           respectively, in the VEC32 mode. It is 64,                                     32 or 16 for the byte and byte9, halfword, or                                  word data sizes, respectively, in the VEC64                                    mode. For scalar operations, NumElem is 0.                           EMASK i!  denotes the element mask for the ith element.                                  It represents 1, 2, or 4 bits in the VGMR0/1,                                  ˜VGMR0/1, VMMR0/1 or ˜VMMR0/1 for byte and                         byte9, halfword or word data sizes,                                            respectively. For scalar operations, the                                       element mask is assumed to be set, even if                                     EMASK i! = 0.                                                        MMASK i!  denotes the element mask for the ith element.                                  It represents 1, 2, or 4 bits in the VMMR0 or                                  VMMR1 for byte and byte9, halfword, or word                                    data sizes, respectively.                                            VCSR      The Vector Control and Status Register                               VCSR<x>   Denotes a bit or bits in VCSR. The "x" is a                                    field name.                                                          VPC       vector processor program counter                                     VECSIZE   vector register size is 32 in VEC32 and 64 in                                  VEC64 mode.                                                          SPAD      scratch pad                                                          ______________________________________                                    

The C programming constructs are used to describe the control-flow of the operations. Exceptions are noted below:

    ______________________________________                                         =           assignment                                                         :           concatenation                                                      {x | | y}                                                                indicates a selection between x or y (not a                                    logical or)                                                        sex         sign-extend to specified data size                                 sex.sub.-- dp                                                                              sign-extend to double precision of specified                                   data size                                                          sign>>      sign-extended (arithmetic) shift right                             zex         zero-extend to specified data size                                 zero>>      zero-extended (logical) shift right                                <<          shift left (zero fill in)                                          trnc7       truncate leading 7 bits (from a halfword)                          trnc1       truncate leading 1 bit (from byte9)                                %           modulo operator                                                    | expression  | absolute value of the expression             /           divide (for float data type, use one of the                                    four IEEE rounding mode)                                           //          divide (uses the round away from zero                                          rounding mode)                                                     saturate ( )                                                                               saturate to the most negative or most                                          positive value, instead of generating                                          overflow, for integer data types. For                                          float data type, the saturation can be                                         to the positive infinity, positive zero,                                       negative zero, or negative infinity.                               ______________________________________                                    

General instruction formats are shown in FIG. 8 and described below.

REAR format is used by the load, store and cache operation instructions, and the fields in the REAR format have the following meanings as given in Table E.13.

                  TABLE E.13                                                       ______________________________________                                         REAR format                                                                    Field   Meaning                                                                ______________________________________                                         Opc<4:0>                                                                               Opcode                                                                 B       Bank identifier for the Rn register.                                   D       Destination/source scalar register. When set,                                  Rn<4:0> denotes a scalar register.                                             The legal values for B:D encodings in the VEC32                                mode are:                                                                      00  Rn is a vector register in the current bank                                01  Rn is a scalar register (in the current bank)                              10  Rn is a vector register in the alternate bank                              11  undefined                                                                  The legal values for B:D encodings in the VEC64 mode                           are:                                                                           00  Only 4, 8, 16 or 32 bytes in the vector                                       register Rn is used                                                         01  Rn is a scalar register                                                    10  All 64 bytes of vector register Rn is used                                 11  undefined                                                          TT<1:0> Transfer Type indicates a specific load or store                               operation. See the LT and ST encoding tables below.                    C       Cache off. Set this bit to bypass data cache for                               load. This bit is set with cache-off mnemonics of                              the load & store instructions (concatenate OFF to                              the mnemonic).                                                         A       Address update. Set this bit to update SRb with the                            effective address. The effective address is                                    calculated as Srb+SRi.                                                 Rn<4:0> Destination/source register number.                                    SRb<4:0>                                                                               Scalar base register number.                                           SRi<4:0>                                                                               Scalar index register number.                                          ______________________________________                                    

Bits 17:15 are reserved and should be zeros to ensure compatibility with future extensions in the architecture. Certain encodings of the B:D and TT fields are undefined.

Programmer should not use these encodings since the architecture does not specify the expected result when such an encoding is used. Table E.14 shows scalar load operations supported (encoded in the TT field as LT) in both VEC32 and VEC64 modes.

                  TABLE E.14                                                       ______________________________________                                         REAR Load Ops in VEC32 and VEC64 Modes                                         D:LT    Mnemonic  Meaning                                                      ______________________________________                                         1 00    .bs9      load 8-bit into byte9 size, sign-extend                      1 01    .h        load 16 bits into halfword size                              1 10    .bz9      load 8-bits into byte9 size, zero-extended                   1 11    .w        load 32 bits into word size                                  ______________________________________                                    

Table E.15 shows vector load operations supported (encoded in the TT field as LT) in VEC32 mode, which is when bit VCSR<0> is clear.

                  TABLE E.15                                                       ______________________________________                                         REAR Load Ops in VEC32 Mode                                                    D:LT  Mnemonic  Meaning                                                        ______________________________________                                         0 00  .4        Load 4 bytes from memory into lower 4 byte9s                                   in register and leave the remaining byte9s                                     unmodified. Every 9th bit of the 4 byte9s                                      are sign-extended from the corresponding 8th                                   bit.                                                           0 01  .8        Load 8 bytes from memory into lower 8 byte9s                                   in register and leave the remaining byte9s                                     unmodified. Every 9th bit of the 8 byte9s                                      are sign-extended from the corresponding 8th                                   bit.                                                           0 10  .16       Load 16 bytes from memory into lower 16 byte                                   9s in register and leave the remaining byte9s                                  unmodified. Every 9th bit of the 16 byte9s                                     are sign-extended from the corresponding 8th                                   bit.                                                           0 11  .32       Load 32 bytes from memory into lower 32                                        byte9s in register and leave the remaining                                     byte9s unmodified. Every 9th bit of the 32                                     byte9s are sign-extended from the                                              corresponding 8th bit.                                         ______________________________________                                    

B bit is used to indicate current or alternate bank.

Table E.16 shows vector load operations supported (encoded in TT field as LT) in VEC64 mode, which is when VCSR<0> bit is set.

                  TABLE E.16                                                       ______________________________________                                         REAR Load Ops in VEC32 Mode                                                    B:D:LT  Mnemonic  Meaning                                                      ______________________________________                                         0 0 00  .4        Load 4 bytes from memory into lower 4                                          byte9s in register and leave the remaining                                     byte9s unmodified. Every 9th bit of the 4                                      byte9s are sign-extended from the                                              corresponding 8th bit.                                       0 0 01  .8        Load 8 bytes from memory into lower 8                                          byte9s in register and leave the remaining                                     byte9s unmodified. Every 9th bit of the 8                                      byte9s are sign-extended from the                                              corresponding 8th bit.                                       0 0 10  .16       Load 16 bytes from memory into lower 16                                        byte9s in register and leave the remaining                                     byte9s unmodified. Every 9th bit of the 16                                     byte9s are sign-extended from the                                              corresponding 8th bit.                                       0 0 11  .32       Load 32 bytes from memory into lower 32                                        byte9s in register and leave the remaining                                     byte9s unmodified. Every 9th bit of the 32                                     byte9s are sign-extended from the                                              corresponding 8th bit.                                       1 0 00            undefined                                                    1 0 01            undefined                                                    1 0 10            undefined                                                    1 0 11  .64       Load 64 bytes from memory into lower 64                                        byte9s in register and leave the remaining                                     byte9s unmodified. Every 9th bit of the 64                                     byte9s are sign-extended from the                                              corresponding 8th bit.                                       ______________________________________                                    

Bit B is used to indicate 64 byte vector operation, since the concept of current and alternate bank does not exist in VEC64 mode.

Table E.17 lists scalar store operations supported (encoded in the TT field as ST) in both VEC32 and VEC64 modes.

                  TABLE E.17                                                       ______________________________________                                         REAR Scalar Store Operations                                                   D:ST     Mnemonic   Meaning                                                    ______________________________________                                         1 00     .b         store byte or byte9 sizes into 8-bits                                          (truncate 1 bit from byte9)                                1 01     .h         store halfword size into 16-bits                           1 10                undefined                                                  1 11     .w         store word size into 32-bits                               ______________________________________                                    

Table E.18 lists the vector store operations supported (encoded in the TT field as ST) in VEC32 mode, which is when VCSR<0> bit is clear.

                  TABLE E.18                                                       ______________________________________                                         REAR Vector Store Operations in VEC32 Mode                                     D:ST   Mnemonic   Meaning                                                      ______________________________________                                         0 00   .4         Store 4 bytes from register to memory.                                         Every 9th bit of the 4 byte9s in register                                      are ignored.                                                 0 01   .8         Store 8 bytes from register to memory.                                         Every 9th bit of the 8 byte9s in register                                      are ignored.                                                 0 10   .16        Store 16 bytes from register to memory.                                        Every 9th bit of the 16 byte9s in register                                     are ignored.                                                 0 11   .32        Store 32 bytes from register to memory.                                        Every 9th bit of the 32 byte9s in register                                     are ignored.                                                 ______________________________________                                    

Table E.19 lists vector store operations supported (encoded in the TT field as ST) in VEC64 mode, which is when VCSR<0> bit is set.

                  TABLE E.19                                                       ______________________________________                                         REAR Vector Store Operations in VEC32 Mode                                     B:D:ST  Mnemonic   Meaning                                                     ______________________________________                                         0 0 00  .4         Store 4 bytes from register to memory.                                         Every 9th bit of the 4 byte9s in register                                      are ignored.                                                0 0 01  .8         Store 8 bytes from register to memory.                                         Every 9th bit of the 8 byte9s in register                                      are ignored.                                                0 0 10  .16        Store 16 bytes from register to memory.                                        Every 9th bit of the 16 byte9s in register                                     are ignored.                                                0 0 11  .32        Store 32 bytes from register to memory.                                        Every 9th bit of the 32 byte9s in register                                     are ignored.                                                1 0 00             undefined                                                   1 0 01             undefined                                                   1 0 10             undefined                                                   1 0 11  .64        Store 64 bytes from register to memory.                                        Every 9th bit of the 64 byte9s in register                                     are ignored.                                                ______________________________________                                    

Bit B is used to indicate 64 byte vector operation, since the concept of current and alternate bank does not exist in VEC64 mode.

REAI format is used by the load, store and cache operation instructions. Table E.20 shows the meanings of the fields in the REAI format.

                  TABLE E.20                                                       ______________________________________                                         REAI format                                                                    Field    Meaning                                                               ______________________________________                                         Opc<4:0> Opcode                                                                B        Bank identifier from the Rn register. When set in                              VEC32 mode, Rn<4:0> denotes a vector register number                           in the alternate bank. When set in VEC64 mode,                                 denotes a full vector (64 byte) operation.                            D        Destination/source scalar register. When set, Rn<4:0>                          denotes a scalar register.                                                     The legal values for B:D encodings in VEC32 mode are:                          00  Rn is a vector register in the current bank                                01  Rn is a scalar register (in the current bank)                              10  Rn is a vector register in the alternate bank                              11  undefined                                                                  The legal values for B:D encodings in VEC64 mode are:                          00  Only 4, 8, 16 or 32 bytes of the vector register                              Rn is used                                                                  01  Rn is a scalar register                                                    10  All 64 bytes of vector register Rn is used                                 11  undefined                                                         TT<1:0>  Transfer Type indicates a specific load or store                               operation. See the LT and ST encoding tables below.                   C        Cache off. Set this bit to bypass data cache for                               load. This bit is set with the cache-off mnemonics of                          the load & store instructions (concatenate OFF to the                          mnemonic).                                                            A        Address update. Set this bit to update SRb with the                            effective address. The effective address is                                    calculated as SRb+IMM<7:0>.                                           Rn<4:0>  Destination/source register number.                                   SRb<4:0> Scalar base register number.                                          IMM<7:0> An 8-bit immediate offset, interpreted as a two's                              complement number.                                                    ______________________________________                                    

The REAR and REAI formats use identical encodings for the transfer types. Refer to the REAR format for further encoding detail.

RRRM5 format provides three register or two registers and a 5-bit immediate operands. Table E.21 defines the filed for the RRRM5 format.

                  TABLE E.21                                                       ______________________________________                                         RRRM5 Format                                                                   Field     Meaning                                                              ______________________________________                                         Op<4:0>   Opcode                                                               D         Destination scalar register. When set, Rd<4:0>                                 denotes a scalar register. When clear, Rd<4:0>                                 denotes a vector register.                                           S         Scalar Rb register. When set indicates that Rb<4:0>                            is a scalar register. When clear, Rb<4:0> is a                                 vector register.                                                     DS<1:0>   Data Size. The encodings are:                                                  00  byte (used by int8 data type)                                              01  byte9 (used by int9 data type)                                             10  halfword (used by int16 data type)                                         11  word (used by int32 or float data type)                          M         Modifier for the D:S bits. See the D:S:M encoding                              table below.                                                         Rd<4:0>   Destination D register number.                                       Ra<4:0>   Source A register number.                                            Rb<4:0> or                                                                               Source B register number or a 5-bit immediate,                       IM5<4:0>  determined by the D:S:M encoding. The 5-bit                                    immediate is interpreted as an unsigned number.                      ______________________________________                                    

Bits 19:15 are reserved and must be zeros to ensure compatibility with future extensions in the architecture.

All vector register operands refer to the current bank (which could either be bank 0 or bank 1) unless stated otherwise. Table E.22 lists the D:S:M encodings when DS<1:0> is 00, 01 or 10.

                  TABLE E.22                                                       ______________________________________                                         RRRM5 D:S:M Encodings for DS not equal 11                                      Encoding                                                                              Rd      Ra      Rb/IM5                                                                               Comments                                          ______________________________________                                         000    VRd     VRa     VRb   Three vector register operands                    001                          undefined                                         010    VRd     VRa     SRb   B operand is a scalar register                    011    VRd     VRa     IM5   B operand is a 5-bit immediate                    100                          undefined                                         101                          undefined                                         110    SRd     SRa     SRb   Three scalar register operands                    111    SRd     SRa     IM5   B operand is 5-bit immediate                      ______________________________________                                    

The D:S:M encodings have the following meanings when DS<1:0> is 11:

                  TABLE E.23                                                       ______________________________________                                         RRRM5 D:S:M Encodings for DS equal 11                                                                Rb/                                                      D:S:M Rd      Ra      IM5  Comments                                            ______________________________________                                         000    VRd    VRa    VRb  Three vector register operands (int32)               001    VRd    VRa    VRb  Three vector register operands (float)               010    VRd    VRa    SRb  B operand is a scalar register (int32)               011    VRd    VRa    IM5  B operand is a 5-bit immediate (int32)               100    VRd    VRa    SRb  B operand is a scalar register (float)               101    SRb    SRa    SRb  Three scalar register operands (float)               110    SRd    SRa    SRb  Three scalar register operands (int32)               111    SRd    SRa    IM5  B operand is a 5-bit immediate                       ______________________________________                                                                   (int32)                                         

RRRR format provides four register operands. Table E.24 shows the fields in the RRRR format.

                  TABLE E.24                                                       ______________________________________                                         RRRR Format                                                                    Field    Meaning                                                               ______________________________________                                         Op<4:0>  Opcode                                                                5        Scalar Rb register. When set indicates that Rb<4:0>                            is a scalar register. When clear, Rb<4:0> is a                                 vector register.                                                      DS<1:0>  Data Size. The encodings are:                                                  00  byte (used by int8 data type)                                              01  byte9 (used by int9 data type)                                             10  halfword (used by int16 data type)                                         11  word (used by int32 or float data type)                           Rc<4:0>  Source/destination C register number.                                 Rd<4:0>  Destination D register number.                                        Rd<4:0>  Source A register number.                                             Rd<4:0>  Source B register number.                                             ______________________________________                                    

All vector register operands refer to the current bank (which could either be bank 0 or bank 1) unless stated otherwise.

RI Format is used only by the load immediate instruction. Table E.25 indicates the fields in the RI format.

                  TABLE E.25                                                       ______________________________________                                         RI Format                                                                      Field      Meaning                                                             ______________________________________                                         D          Destination scalar register. When set, Rd<4:0>                                 denotes a scalar register. When clear, Rd<4:0>                                 denotes a vector register in the current bank.                      F          Float data type. When set, denotes the floating                                point data type, and requires DS<1:0> to be 11.                     DS<1:0>    Data Size. The encodings are:                                                  00  byte (used by int8 data type)                                              01  byte9 (used by int9 data type)                                             10  halfword (used by int16 data type)                                         11  word (used by int32 or float data type)                         Rd<4.0>    Destination D register number.                                      IMM<18:0>  A 19-bit immediate value.                                           ______________________________________                                    

Certain encodings of the F:DS<1:0> field are undefined. Programmer should not use these encodings since the architecture does not specify the expected result when such an encoding is used. The value loaded into Rd depends on the data type, as shown in Table E.26.

                  TABLE E.26                                                       ______________________________________                                         RI Format Loaded Values                                                        Format Data type    Register Operand                                           ______________________________________                                         .b     byte (8-bit) Rd<7:0>:=Imm<7:0>                                          .b9    byte9 (9-bit)                                                                               Rd<8:0>:=Imm<8:0>                                          .h     halfword (16-bit)                                                                           Rd<15:0>:=Imm<15:0>                                        .w     word (32-bit)                                                                               Rd<31:0>:=sign-extend Imm<18:0>                            .f     floating point                                                                              Rd <31>:=Imm<18>(sign)                                            (32-bit)     Rd <30:23>:=Imm<17.0>(exponent)                                                Rd <22:13>:=Imm<9.0>(mantissa)                                                 Rd <12:0>:=zeroes                                          ______________________________________                                    

CT Format includes the fields shown in Table E.27.

                  TABLE E.27                                                       ______________________________________                                         CT Format                                                                      Field      Meaning                                                             ______________________________________                                         Opc<3:0>   Opcode                                                              Cond<2:0>  Branch condition:                                                              000  always                                                                    001  less than                                                                 010  equal                                                                     011  less than or equal                                                        100  greater than                                                              101  not equal                                                                 110  greater than or equal                                                     111  overflow                                                       IMM<22:0>  A 23-bit immediate word offset, interpreted as a                               two's complement number.                                            ______________________________________                                    

The branch conditions use VCSR GT:EQ:LT! field. The overflow condition uses the VCSR SO! bit, which preceeds the GT, EQ and LT bits when set. The VCCS and VCBARR interprets the Cond<2:0> field differently than as description above. Refer to their instruction description detail.

RRRM9 format specifies three registers or two registers and a 9-bit immediate operands. Table E.28 indicates the fields of the RRRM9 format.

                  TABLE E.28                                                       ______________________________________                                         RRRM9 Format                                                                   Field    Meaning                                                               ______________________________________                                         Opc<5:0> Opcode                                                                D        Destination scalar register. When set, Rd<4:0>                                 denotes a scalar register. When clear, Rd<4:0>                                 denotes a vector register.                                            S        Scalar Rb register. When set indicates that Rb<4:0>                            is a scalar register. When clear, Rb<4:0> is a                                 vector register.                                                      DS<1:0>  Data Size. The encodings are:                                                  00 byte (used by int8 data type)                                               01 byte9 (used by int9 data type)                                              10 halfword (used by int16 data type)                                          11 word (used by int32 or float data type)                            M        Modifier for the D:S bits. See the D:S:M encoding                              table below.                                                          Rd<4:0>  Destination register number.                                          Ra<4:0>  Source A register number.                                             Rb<4:0> or                                                                              Source B register number or a 5-bit immediate,                        IM5<4:0> determined by the D:S:M encoding.                                     IM9<3:0> Together with IM5<4:0> provides a 9-bit immediate,                             determined by the D:S:M encoding.                                     ______________________________________                                    

Bits 19:15 are reserved when the D:S:M encoding does not specify an immediate operand and must be zeros to ensure future compatibility.

All vector register operands refer to the current bank (which could either be bank 0 or bank 1) unless stated otherwise. D:S:M encodings are identical to those shown in Tables E.22 and E.23 for the RRRM5 format except that immediate values extracted from the immediate field depends on the DS<1:0> encoding, as shown in Table E.29.

                  TABLE E.29                                                       ______________________________________                                         Immediate Values in RRRM9 Format                                                     Matching                                                                 DS    Data Type B Operand                                                      ______________________________________                                         00    int8      Source B<7:0>:= IM9<2:0>: IM5<4:0>                             01    int9      Source B<8:0>:= IM9<3:0>: IM5<4:0>                             10    int16     Source B<15:0>:= sex(IM9<3:0>: IM5<4:0>)                       11    int32     Source B<31:0>:= sex(IM9<3:0>: IM5<4:0>)                       ______________________________________                                    

The immediate format is not available with the float data type.

In the following, the MSP vector instructions appear in the alphabetical order. Note:

1. An instruction is affected by the element mask, unless noted otherwise. CT format instructions are not affected by the element mask. REAR and REAI format instructions, which consists of the load, store and cache instructions, are also not affected by the element mask.

2. The 9-bit immediate operand is not available with float data type.

3. In the Operation description, only the vector form is given. For scalar operation, assume only one, the 0th, element is defined.

4. For RRRMS and RRRM9 formats, the following encodings are used for integer data types (b, b9, h, w):

    ______________________________________                                         D:S:M 000        010    011      110  111                                      DS    00         01     10       11                                            ______________________________________                                    

5. For RRRM5 and RRRM9 formats, the following encodings are used for float data type:

    ______________________________________                                         D:S:M 001        100    n/a      101  n/a                                      DS                                    11                                       ______________________________________                                    

6. For all instructions that can cause an overflow, saturation to int8, int9, int16, int32 maximum or minimum limits are applied when VCSR<ISAT> bit is set. Correspondingly, floating point result is saturated to -infinity, -zero, +zero or +infinity when VCSR<FSAT> bit is set.

7. Syntactically, .n may be used instead of .b9 to denote the byte9 data size.

8. For all instructions, the floating point result returned to the destination register or to the vector accumulator is of the IEEE 754 single precision format. The floating point result is written to the lower portion of the accumulator and the upper portion is not modified. ##SPC1## 

We claim:
 1. A vector processor comprising:a first bank of vector registers, wherein each vector register numbers assigned to other vector registers in the first bank; a second bank of vector registers, wherein each vector register in the second bank is assigned a register number which is distinct from register numbers assigned to other vector registers in the second bank but is the same as a register number assigned to a corresponding vector register in the first bank; a control register which includes a first field, the first field storing a value that identifies one of the first and second banks as a default bank; and selection circuitry for first and second banks of vector registers, wherein the selection circuitry is operable in a first mode to access a vector register that is in the default bank and is identified by a register number from an instruction being executed by the vector processor.
 2. The vector processor of claim 1, wherein:the selection circuitry is operable in a second mode to access a first vector register from the first bank and a second vector register from the second bank, the first and second vector registers having been assigned a first register number; and for execution of an instruction that contains the first register number, a combination of the first and second register is used for a vector value bigger than could be stored in the first vector register.
 3. The vector processor of claim 2, wherein the selection circuitry is operable in a third mode to access a vector register identified by combination of a register number and a bank value from an instruction being executed by the vector processor.
 4. The vector processor of claim 1, wherein the selection circuitry is operable in a second mode to access a vector register identified by combination of a register number and a bank value from an instruction being executed by the vector processor.
 5. The vector processor of claim 4, wherein the selection circuitry operates in the first mode for instructions representing logic operations performed on vector quantities, and in the second mode for load/store operations.
 6. A method for operation a vector processor, comprising:assigning register numbers to vector registers in a first bank, wherein for each vector register in the first bank the assigned register number is distinct from register numbers assigned to other vector registers in the first bank; assigning register numbers to vector registers in a second bank, wherein for each vector register in the second bank the assigned register number is distinct from register numbers assigned to other vector registers in the second bank and is the same as a register number assigned to a corresponding vector register in the first bank; and executing a first instruction that includes a register number, wherein executing the instruction includes accessing a vector register that is assigned the register number included in the first instruction and is in a bank indicated by a field of a control register of the vector processor.
 7. The method of claim 6, further comprising executing a second instruction which includes a second register number , wherein executing the second instruction includes accessing a first vector register that is assigned the second register number and is in the first bank, and accessing a second vector register that is assigned the second register number and is in the second bank.
 8. The method of claim 7, wherein accessing the first and second vector registers comprising processing a single vector which has a first set of data elements stored in the first vector register and a second set of data elements stored in the second vector register.
 9. The method of claim 7, further comprising executing a third instruction that includes a third register number and a bank identifier, wherein executing the third instruction includes accessing a vector register that is assigned the third register number, the bank identifier identifying which of the first and second banks contains the vector register accessed.
 10. The method of claim 6, further comprising executing a second instruction that includes a second register number and a bank identifier, wherein executing the second instruction includes accessing a vector register that is assigned the second register number, the bank identifier identifying which of the first and second banks contains the vector register accessed.
 11. The method of claim 6, further comprising executing a second instruction before executing the first instruction, wherein executing the second instruction loads into the field of the control register a value that selects which of the first and second banks is used in executing the first instruction.
 12. The vector processor of claim 1, wherein when the selection circuit operates in the first mode, the instruction being executed does not indicate whether the vector register accessed is in the first or second bank.
 13. The vector processor of claim 1, wherein the combination of the first and second register is used for a vector value having more elements than could be stored in the first vector register. 